diff --git a/modules/openapi-generator/src/main/resources/csharp/ApiClient.mustache b/modules/openapi-generator/src/main/resources/csharp/ApiClient.mustache
index 053865e0c91a..bad3fbfa9cb2 100644
--- a/modules/openapi-generator/src/main/resources/csharp/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/ApiClient.mustache
@@ -29,7 +29,6 @@ using Polly;
 {{#hasOAuthMethods}}
 using {{packageName}}.Client.Auth;
 {{/hasOAuthMethods}}
-using {{packageName}}.{{modelPackage}};
 
 namespace {{packageName}}.Client
 {
@@ -70,10 +69,10 @@ namespace {{packageName}}.Client
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is {{{packageName}}}.{{modelPackage}}.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return (({{{packageName}}}.{{modelPackage}}.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -504,7 +503,7 @@ namespace {{packageName}}.Client
                 {{/throwOnAnyError}}
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof({{{packageName}}}.{{modelPackage}}.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/modules/openapi-generator/src/main/resources/csharp/ApiClient.v790.mustache b/modules/openapi-generator/src/main/resources/csharp/ApiClient.v790.mustache
index adcb2d15c8bc..d2f74ed945d4 100644
--- a/modules/openapi-generator/src/main/resources/csharp/ApiClient.v790.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/ApiClient.v790.mustache
@@ -29,7 +29,6 @@ using Polly;
 {{#hasOAuthMethods}}
 using {{packageName}}.Client.Auth;
 {{/hasOAuthMethods}}
-using {{packageName}}.{{modelPackage}};
 
 namespace {{packageName}}.Client
 {
@@ -70,10 +69,10 @@ namespace {{packageName}}.Client
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is {{{packageName}}}.{{modelPackage}}.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return (({{{packageName}}}.{{modelPackage}}.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -496,7 +495,7 @@ namespace {{packageName}}.Client
                 {{/throwOnAnyError}}
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof({{{packageName}}}.{{modelPackage}}.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/modules/openapi-generator/src/main/resources/csharp/validatable.mustache b/modules/openapi-generator/src/main/resources/csharp/validatable.mustache
index 34693f6c14f5..97220211efc8 100644
--- a/modules/openapi-generator/src/main/resources/csharp/validatable.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/validatable.mustache
@@ -4,7 +4,7 @@
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -14,7 +14,7 @@
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
 {{/discriminator}}
 {{^discriminator}}
@@ -24,7 +24,7 @@
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -34,7 +34,7 @@
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
   {{/parent}}
   {{^parent}}
@@ -43,7 +43,7 @@
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
   {{/parent}}
 {{/discriminator}}
@@ -62,7 +62,7 @@
             // {{{name}}} ({{{dataType}}}) not enum
             if ({{{vendorExtensions.x-csharp-not-enum-comparison}}})
             {
-                yield return new ValidationResult("Invalid value for {{{name}}}, must not be a value excluded by the 'not' schema.", new [] { "{{{name}}}" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for {{{name}}}, must not be a value excluded by the 'not' schema.", new [] { "{{{name}}}" });
             }
 
             {{/vendorExtensions.x-csharp-not-enum-comparison}}
@@ -75,7 +75,7 @@
             // {{{name}}} ({{{dataType}}}) maxLength
             if (this.{{{name}}} != null && this.{{{name}}}.Length > {{maxLength}})
             {
-                yield return new ValidationResult("Invalid value for {{{name}}}, length must be less than {{maxLength}}.", new [] { "{{{name}}}" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for {{{name}}}, length must be less than {{maxLength}}.", new [] { "{{{name}}}" });
             }
 
             {{/maxLength}}
@@ -83,7 +83,7 @@
             // {{{name}}} ({{{dataType}}}) minLength
             if (this.{{{name}}} != null && this.{{{name}}}.Length < {{minLength}})
             {
-                yield return new ValidationResult("Invalid value for {{{name}}}, length must be greater than {{minLength}}.", new [] { "{{{name}}}" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for {{{name}}}, length must be greater than {{minLength}}.", new [] { "{{{name}}}" });
             }
 
             {{/minLength}}
@@ -94,7 +94,7 @@
             // {{{name}}} ({{{dataType}}}) maximum
             if ({{#useGenericHost}}{{^required}}this.{{{name}}}Option.IsSet && {{/required}}{{/useGenericHost}}this.{{{name}}}{{#useGenericHost}}{{^required}}Option.Value{{/required}}{{/useGenericHost}} {{#exclusiveMaximum}}<={{/exclusiveMaximum}}{{^exclusiveMaximum}}>{{/exclusiveMaximum}} ({{{dataType}}}){{maximum}})
             {
-                yield return new ValidationResult("Invalid value for {{{name}}}, must be a value less than {{^exclusiveMaximum}}or equal to {{/exclusiveMaximum}}{{maximum}}.", new [] { "{{{name}}}" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for {{{name}}}, must be a value less than {{^exclusiveMaximum}}or equal to {{/exclusiveMaximum}}{{maximum}}.", new [] { "{{{name}}}" });
             }
 
             {{/maximum}}
@@ -102,7 +102,7 @@
             // {{{name}}} ({{{dataType}}}) minimum
             if ({{#useGenericHost}}{{^required}}this.{{{name}}}Option.IsSet && {{/required}}{{/useGenericHost}}this.{{{name}}}{{#useGenericHost}}{{^required}}Option.Value{{/required}}{{/useGenericHost}} {{#exclusiveMaximum}}>={{/exclusiveMaximum}}{{^exclusiveMaximum}}<{{/exclusiveMaximum}} ({{{dataType}}}){{minimum}})
             {
-                yield return new ValidationResult("Invalid value for {{{name}}}, must be a value greater than {{^exclusiveMinimum}}or equal to {{/exclusiveMinimum}}{{minimum}}.", new [] { "{{{name}}}" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for {{{name}}}, must be a value greater than {{^exclusiveMinimum}}or equal to {{/exclusiveMinimum}}{{minimum}}.", new [] { "{{{name}}}" });
             }
 
             {{/minimum}}
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/csharpnetcore/CSharpClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/csharpnetcore/CSharpClientCodegenTest.java
index 4714f6ddb027..c9ef432cf1ff 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/csharpnetcore/CSharpClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/csharpnetcore/CSharpClientCodegenTest.java
@@ -304,7 +304,7 @@ public void testNotEnumConstraintIsEnforced() throws IOException {
                 "throw new ArgumentException(\"Invalid value for Kind, must not be a value excluded by the 'not' schema.\");");
         // Also enforced in Validate() for explicit validation.
         assertFileContains(other,
-                "yield return new ValidationResult(\"Invalid value for Kind, must not be a value excluded by the 'not' schema.\", new [] { \"Kind\" });");
+                "yield return new System.ComponentModel.DataAnnotations.ValidationResult(\"Invalid value for Kind, must not be a value excluded by the 'not' schema.\", new [] { \"Kind\" });");
         // The Known member (plain enum) must NOT get the not-enum handling.
         assertFileNotContains(Paths.get(output.getAbsolutePath(), "src", "Org.OpenAPITools", "Model", "Known.cs"),
                 "must not be a value excluded by the 'not' schema");
@@ -876,6 +876,45 @@ public void testValueTypeConstructorUnchangedWithoutConditionalSerialization() t
         assertFileNotContains(updateCommand.toPath(), "_flagAutoRenew");
     }
 
+    @Test(description = "restsharp ApiClient does not import the model namespace, so schemas named Parameter, ParameterType or Task do not collide with RestSharp/System types")
+    public void testRestSharpApiClientDoesNotImportModelNamespace() throws IOException {
+        Map<String, File> files = generateModelNameCollisions();
+
+        File apiClient = files.get("ApiClient.cs");
+        assertNotNull(apiClient);
+        assertFileNotContains(apiClient.toPath(), "using Org.OpenAPITools.Model;");
+        assertFileContains(apiClient.toPath(), "obj is Org.OpenAPITools.Model.AbstractOpenAPISchema");
+    }
+
+    @Test(description = "a schema named ValidationResult does not hide the DataAnnotations type in generated models")
+    public void testValidatableModelsQualifyValidationResult() throws IOException {
+        Map<String, File> files = generateModelNameCollisions();
+
+        File model = files.get("ValidationResult.cs");
+        assertNotNull(model);
+        assertFileContains(model.toPath(),
+                "IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)",
+                "yield return new System.ComponentModel.DataAnnotations.ValidationResult(");
+        assertFileNotContains(model.toPath(), "IEnumerable<ValidationResult>", "new ValidationResult(");
+    }
+
+    private Map<String, File> generateModelNameCollisions() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/csharp/model-name-collisions.yaml");
+        final DefaultGenerator defaultGenerator = new DefaultGenerator();
+        final ClientOptInput clientOptInput = new ClientOptInput();
+        clientOptInput.openAPI(openAPI);
+        CSharpClientCodegen cSharpClientCodegen = new CSharpClientCodegen();
+        cSharpClientCodegen.setLibrary("restsharp");
+        cSharpClientCodegen.setOutputDir(output.getAbsolutePath());
+        clientOptInput.config(cSharpClientCodegen);
+        defaultGenerator.opts(clientOptInput);
+
+        return defaultGenerator.generate().stream()
+                .collect(Collectors.toMap(File::getName, Function.identity(), (first, second) -> first));
+    }
+
     private Map<String, File> generateConditionalSerializationValueTypeModels(boolean conditionalSerialization) throws IOException {
         File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
         output.deleteOnExit();
diff --git a/modules/openapi-generator/src/test/resources/3_0/csharp/model-name-collisions.yaml b/modules/openapi-generator/src/test/resources/3_0/csharp/model-name-collisions.yaml
new file mode 100644
index 000000000000..6be3658793a2
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/csharp/model-name-collisions.yaml
@@ -0,0 +1,38 @@
+openapi: 3.0.3
+info:
+  title: Schemas named like framework types
+  version: 1.0.0
+paths:
+  /tasks:
+    get:
+      operationId: getTask
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Task'
+components:
+  schemas:
+    Task:
+      type: object
+      properties:
+        parameter:
+          $ref: '#/components/schemas/Parameter'
+        validation:
+          $ref: '#/components/schemas/ValidationResult'
+    Parameter:
+      type: object
+      properties:
+        type:
+          $ref: '#/components/schemas/ParameterType'
+    ParameterType:
+      type: string
+      enum: [text, number]
+    ValidationResult:
+      type: object
+      properties:
+        message:
+          type: string
+          maxLength: 100
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Client/ApiClient.cs
index 09d4c2af7b29..5d46b39fe2af 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -30,7 +30,6 @@
 using RestSharpMethod = RestSharp.Method;
 using FileIO = System.IO.File;
 using Polly;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -71,10 +70,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -479,7 +478,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Bird.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Bird.cs
index aa2a56ead0b0..6447c7cd8dad 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Bird.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Bird.cs
@@ -138,7 +138,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Category.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Category.cs
index d38d7b9c68d0..9d730cc2d813 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Category.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/DataQuery.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/DataQuery.cs
index bfb232e51a7a..b41b1cc92045 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/DataQuery.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/DataQuery.cs
@@ -165,7 +165,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -175,7 +175,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in BaseValidate(validationContext))
             {
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/DefaultValue.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/DefaultValue.cs
index 714405059c41..ab596828e9c9 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/DefaultValue.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/DefaultValue.cs
@@ -278,7 +278,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/NumberPropertiesOnly.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/NumberPropertiesOnly.cs
index 385596a2a36a..a82966e03715 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/NumberPropertiesOnly.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/NumberPropertiesOnly.cs
@@ -144,18 +144,18 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Double (double) maximum
             if (this.Double > (double)50.2)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 50.2.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 50.2.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)0.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 0.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 0.8.", new [] { "Double" });
             }
 
             yield break;
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Pet.cs
index d3f322a33a2a..c9ad84f5d694 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Pet.cs
@@ -252,7 +252,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Query.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Query.cs
index 8f4c27048fb4..d878e06fb5f6 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Query.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Query.cs
@@ -161,7 +161,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Tag.cs
index 714707308320..a60cff50c616 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/Tag.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestFormObjectMultipartRequestMarker.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestFormObjectMultipartRequestMarker.cs
index 6b7ad657490e..688d42863d4d 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestFormObjectMultipartRequestMarker.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestFormObjectMultipartRequestMarker.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter.cs
index 4d83efa57363..436484c3a421 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter.cs
@@ -176,7 +176,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.cs
index 7cdfe8797c55..4b0964c756d2 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Client/ApiClient.cs
index d53a640efdd3..96656d4c36c9 100644
--- a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -30,7 +30,6 @@
 using RestSharpMethod = RestSharp.Method;
 using FileIO = System.IO.File;
 using Polly;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -71,10 +70,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -479,7 +478,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartArrayRequest.cs b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartArrayRequest.cs
index bb1e4d0eda6b..cebfd4306786 100644
--- a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartArrayRequest.cs
+++ b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartArrayRequest.cs
@@ -112,7 +112,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartExtraAnnotationRequest.cs b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartExtraAnnotationRequest.cs
index ce3c83b197ef..a46f49e1736b 100644
--- a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartExtraAnnotationRequest.cs
+++ b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartExtraAnnotationRequest.cs
@@ -122,7 +122,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartMixedRequest.cs b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartMixedRequest.cs
index 17a5fc53f5ef..c9b91a46244f 100644
--- a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartMixedRequest.cs
+++ b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartMixedRequest.cs
@@ -158,7 +158,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartMixedRequestMarker.cs b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartMixedRequestMarker.cs
index c45b340cb890..7bfb15a3e065 100644
--- a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartMixedRequestMarker.cs
+++ b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartMixedRequestMarker.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartSingleRequest.cs b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartSingleRequest.cs
index b507ac9ea6a4..519a87b4e956 100644
--- a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartSingleRequest.cs
+++ b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Model/MultipartSingleRequest.cs
@@ -112,7 +112,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/AnyOfStringArrayOfString.cs b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/AnyOfStringArrayOfString.cs
index 9d8bd7486d2c..a96f7c4d342f 100644
--- a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/AnyOfStringArrayOfString.cs
+++ b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/AnyOfStringArrayOfString.cs
@@ -86,7 +86,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef.cs b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef.cs
index 58063242f246..0e1fc8ea2e9f 100644
--- a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef.cs
+++ b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef2.cs b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef2.cs
index 51e049378b77..f3e3b9a436ac 100644
--- a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef2.cs
+++ b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef2.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef3.cs b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef3.cs
index 057241873673..204281c2a654 100644
--- a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef3.cs
+++ b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullAndRef3.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullableTest.cs b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullableTest.cs
index aa5a21297a26..e76a910a98a3 100644
--- a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullableTest.cs
+++ b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullableTest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/Parent.cs b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/Parent.cs
index e9082e293178..57acc7f29927 100644
--- a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/Parent.cs
+++ b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/Parent.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithOneOfProperty.cs b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithOneOfProperty.cs
index 8408e7b83152..bd4c836fdb26 100644
--- a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithOneOfProperty.cs
+++ b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithOneOfProperty.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithPluralOneOfProperty.cs b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithPluralOneOfProperty.cs
index 577db1c9ad3e..fb0cb4a58c0d 100644
--- a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithPluralOneOfProperty.cs
+++ b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithPluralOneOfProperty.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithPluralOneOfPropertyNumber.cs b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithPluralOneOfPropertyNumber.cs
index 466839663f6e..3a399c5024a7 100644
--- a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithPluralOneOfPropertyNumber.cs
+++ b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithPluralOneOfPropertyNumber.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/PropertiesWithAnyOf.cs b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/PropertiesWithAnyOf.cs
index 4bbeb83851e3..af53f27cc67a 100644
--- a/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/PropertiesWithAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/PropertiesWithAnyOf.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Model/HelloWorldPostRequest.cs b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Model/HelloWorldPostRequest.cs
index 95d70aa4c80f..7016ba36d0c6 100644
--- a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Model/HelloWorldPostRequest.cs
+++ b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Model/HelloWorldPostRequest.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/Foo.cs
index 96cb3dea0085..c0dbc731279c 100644
--- a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/Foo.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/IconsDefaultResponse.cs b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/IconsDefaultResponse.cs
index 2ee352e594e1..1b1eb0d93d7b 100644
--- a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/IconsDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/IconsDefaultResponse.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/IconsSizeParameter.cs b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/IconsSizeParameter.cs
index 622b404550d4..cf2842f2a7e0 100644
--- a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/IconsSizeParameter.cs
+++ b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Model/IconsSizeParameter.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Color.cs b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Color.cs
index 987e130d0b2a..ce6d956fa0b5 100644
--- a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Color.cs
+++ b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Color.cs
@@ -106,42 +106,42 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // B (int) maximum
             if (this.BOption.IsSet && this.BOption.Value > (int)255)
             {
-                yield return new ValidationResult("Invalid value for B, must be a value less than or equal to 255.", new [] { "B" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for B, must be a value less than or equal to 255.", new [] { "B" });
             }
 
             // B (int) minimum
             if (this.BOption.IsSet && this.BOption.Value < (int)0)
             {
-                yield return new ValidationResult("Invalid value for B, must be a value greater than or equal to 0.", new [] { "B" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for B, must be a value greater than or equal to 0.", new [] { "B" });
             }
 
             // G (int) maximum
             if (this.GOption.IsSet && this.GOption.Value > (int)255)
             {
-                yield return new ValidationResult("Invalid value for G, must be a value less than or equal to 255.", new [] { "G" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for G, must be a value less than or equal to 255.", new [] { "G" });
             }
 
             // G (int) minimum
             if (this.GOption.IsSet && this.GOption.Value < (int)0)
             {
-                yield return new ValidationResult("Invalid value for G, must be a value greater than or equal to 0.", new [] { "G" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for G, must be a value greater than or equal to 0.", new [] { "G" });
             }
 
             // R (int) maximum
             if (this.ROption.IsSet && this.ROption.Value > (int)255)
             {
-                yield return new ValidationResult("Invalid value for R, must be a value less than or equal to 255.", new [] { "R" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for R, must be a value less than or equal to 255.", new [] { "R" });
             }
 
             // R (int) minimum
             if (this.ROption.IsSet && this.ROption.Value < (int)0)
             {
-                yield return new ValidationResult("Invalid value for R, must be a value greater than or equal to 0.", new [] { "R" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for R, must be a value greater than or equal to 0.", new [] { "R" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/ColorOrNull.cs b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/ColorOrNull.cs
index 20cecf34f10e..ac154dffb34f 100644
--- a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/ColorOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/ColorOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/NullTypeDirect.cs b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/NullTypeDirect.cs
index b94b0913878e..e6e618445b55 100644
--- a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/NullTypeDirect.cs
+++ b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/NullTypeDirect.cs
@@ -91,7 +91,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Shape.cs
index adbf35bb161d..0a4a01ab71e9 100644
--- a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 7ad4d0642e24..0dbd9a6c597a 100644
--- a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Widget.cs b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Widget.cs
index 5632d8cbd510..74025e1e986d 100644
--- a/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Widget.cs
+++ b/samples/client/petstore/csharp/generichost/latest/NullTypes/src/Org.OpenAPITools/Model/Widget.cs
@@ -129,7 +129,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Model/OneOfArrayRequest.cs b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Model/OneOfArrayRequest.cs
index 318822e9f2f3..5234000d9fa2 100644
--- a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Model/OneOfArrayRequest.cs
+++ b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Model/OneOfArrayRequest.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Model/TestObject.cs b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Model/TestObject.cs
index 8f154b47cec6..36db65239530 100644
--- a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Model/TestObject.cs
+++ b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Model/TestObject.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Activity.cs
index 9def19eb7ccc..b4c92583c096 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Activity.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 38a0f47c6f50..f2bf49d374b3 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index b77145c6f888..d4885700cae6 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -187,7 +187,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Animal.cs
index 71e1da3abd53..5b43ef1714c2 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Animal.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -92,7 +92,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ApiResponse.cs
index df6620749f69..23a8d5947c38 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -106,7 +106,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Apple.cs
index a8d8ada0ed03..a37ab308644d 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Apple.cs
@@ -106,7 +106,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/AppleReq.cs
index 9e757834af64..62d95cfc1423 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index b026b3b7ea75..f9615beb7810 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 4da1ca573ae1..a9f7e24f7f07 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayTest.cs
index cdbef448f515..77dba91293df 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -106,7 +106,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Banana.cs
index e6337a0cbe25..a14bdb8f1b5f 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Banana.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/BananaReq.cs
index 0bf61002941a..c671be256c0b 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/BasquePig.cs
index 5f0981fe22cb..f842408b5f8c 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -67,7 +67,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Capitalization.cs
index 5dcb942b83c2..02be25062cfa 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -155,7 +155,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Category.cs
index 93c23336f5a5..cf501aa0bd32 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Category.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ClassModel.cs
index f5dd42d7d34e..1b490feded24 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 9bf60f135a54..a3d476c6b198 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DanishPig.cs
index 8963a6916e8b..645ed680380b 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -67,7 +67,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 7974de8c0a7f..7424a46b5134 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 7c29fc9f3440..8fd58f8e3207 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Drawing.cs
index 9a546d9d3d02..f18f2ec10236 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Drawing.cs
@@ -129,7 +129,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EntityBase.cs
index c14bc3cc145f..dd8501b90b33 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -66,7 +66,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -76,7 +76,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EnumArrays.cs
index 0288aae1a9ab..62f2f2948aeb 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -222,7 +222,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EnumTest.cs
index a2e083962f9b..3f8b0d894725 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -678,7 +678,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8730c9005e78..a018df41fd45 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/File.cs
index 4cc9b840f1fe..fd388d713885 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/File.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index f7faeb4f5d47..aa4c6bda9ab9 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Foo.cs
index 96cb3dea0085..c0dbc731279c 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Foo.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 5c35c5963164..7b735892f5f2 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FormatTest.cs
index 0bb9c90e4a9e..b353b70bdc33 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -477,114 +477,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -630,13 +630,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Fruit.cs
index 6ce32fe5b719..243215e72240 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Fruit.cs
@@ -97,7 +97,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FruitReq.cs
index 5924c8e443bd..b28dc4d8ed56 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/GmFruit.cs
index bd0dc42d3bee..5c0e1b8032c1 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -101,7 +101,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 4df21a1883db..7b5ec7968302 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -66,7 +66,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -76,7 +76,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index eee9d949fe26..c92feca22306 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index 0498ecdfecfa..4a6072ea4ce2 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index a30816464b56..e19af6d9564c 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -154,7 +154,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index e6c7dc8e1908..e20a03d9a330 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/List.cs
index c0e317bd750a..a999bfd7d11b 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/List.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index d0b95803f1ce..95bfc0879ecc 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Mammal.cs
index 3c2326670a79..427969287760 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Mammal.cs
@@ -94,7 +94,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -104,7 +104,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MapTest.cs
index c1f80b5c456a..a43785d039f7 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MapTest.cs
@@ -188,7 +188,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 5d6e1e418f6b..8a1c389b54cc 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index 61f06974324f..52b3edcf5245 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -127,7 +127,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 4ea841a71ae2..1b2be02e1ff1 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index e7da5fc3b7c3..9dc1bb0487da 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -124,7 +124,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 8008f6ac248f..3627be0435a4 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -122,7 +122,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedSubId.cs
index 9c59717dcdc4..43b6ed78034c 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Model200Response.cs
index 5934337414cd..7b2d41fa6a65 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ModelClient.cs
index 65ac1757e90a..557a61538eaa 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Name.cs
index 3f861abcf306..2e0a9b6e20f6 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Name.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 14ca17f982ee..639fd9647b04 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableClass.cs
index 7a4976004c34..e5f3d1e1ef87 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -257,7 +257,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index e2fe4c7f4bb5..53b05cbad642 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableShape.cs
index 7a2e48f13871..b7f84ea231cd 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -89,7 +89,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NumberOnly.cs
index 8d4dd0cb7d39..0fc7917e90e7 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index 4ec877b17b12..9faa94a40396 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -125,7 +125,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/OneOfString.cs
index 626368ba9f4e..7cc7a1520b56 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -64,7 +64,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Order.cs
index 15b463eabfe8..d9e7b82089c3 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Order.cs
@@ -237,7 +237,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3de119dd0823..908821deb7ba 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -106,7 +106,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Pet.cs
index ded12e7103ea..44c8d63e4471 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Pet.cs
@@ -223,7 +223,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Pig.cs
index 6498a57907ab..67bf0578d376 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Pig.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -89,7 +89,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 2f4281275b53..eb6f31431a7a 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -109,7 +109,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Quadrilateral.cs
index dc55cf1cfe3f..3006b1d683fe 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -89,7 +89,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 8d3e9ab67d68..5b0c53f3e02c 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -67,7 +67,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 42121416b7fb..b9d9110c9f10 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RequiredClass.cs
index 35aab77b81bc..f011f8392c27 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1690,7 +1690,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Result.cs
index f9b56250e6c0..5d38ca215a0c 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Result.cs
@@ -109,7 +109,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Return.cs
index bec29dd630c1..2072658c391a 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Return.cs
@@ -108,7 +108,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 8562054cd0fd..267f0c2a5292 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 71c93036ae38..adf1f943ae24 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 5bba23900159..15db28a7ace3 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Shape.cs
index 96fb993b385f..475800caf2df 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Shape.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -89,7 +89,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 8c5a4e1255d7..dcef2315b366 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -67,7 +67,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 239c63a2aa1c..560bb6de2586 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -89,7 +89,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 524afe09eb9d..cbe474cbcc2f 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ad0d3ac92e64..196ef3ffbaaf 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Tag.cs
index 821a07b93c85..28d8e4a6b497 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Tag.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 1ed465d65b4f..ccb351cfffd8 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 8b1b4218d67a..4a025608755b 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestDescendants.cs
index eba4c64d0c62..65e07c0d074b 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -141,7 +141,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index abf1e01157d4..28f18bf627e1 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestResult.cs
index 8448ffcae745..f3c2639d5b9b 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TestResult.cs
@@ -108,7 +108,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Triangle.cs
index bc871e72a346..3c1e6dd10261 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Triangle.cs
@@ -94,7 +94,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -104,7 +104,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 8a2b2ddc8dd6..10e1887b4d05 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -67,7 +67,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/User.cs
index 5581589b3750..f835d6cda9ee 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/User.cs
@@ -255,7 +255,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Whale.cs
index 10d1735bdd84..40a76844f717 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Whale.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Zebra.cs
index 6e0e3402908e..a831a847952a 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Zebra.cs
@@ -170,7 +170,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 3dc111404975..bbb387c4f086 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -140,7 +140,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/AllOf/src/Org.OpenAPITools/Model/Person.cs b/samples/client/petstore/csharp/generichost/net10/AllOf/src/Org.OpenAPITools/Model/Person.cs
index a8f07fd13d7a..4373e60686d9 100644
--- a/samples/client/petstore/csharp/generichost/net10/AllOf/src/Org.OpenAPITools/Model/Person.cs
+++ b/samples/client/petstore/csharp/generichost/net10/AllOf/src/Org.OpenAPITools/Model/Person.cs
@@ -106,7 +106,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -116,7 +116,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
index f013ab58aff2..f985f250f712 100644
--- a/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
index d2e3592a7114..b1b959afea24 100644
--- a/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
index d283da3cd5f9..f5af2e0caaf1 100644
--- a/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -109,7 +109,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
index 8cfcda99a1d7..0754094c6901 100644
--- a/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
index 2be6e1b0501c..893a8623dc4f 100644
--- a/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
index ebcf62ab1443..55d4d2ba7126 100644
--- a/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
@@ -108,7 +108,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Activity.cs
index 0baba23ccf52..f51e85f459e9 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 38e288cbbe85..852840c03144 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 8b63e560e3c3..78fd02d9e8fd 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Animal.cs
index 2407c49d6e87..b2d1a75913d7 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
index af6d432b7f9f..dc2f82b08fea 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Apple.cs
index e9c5013017fa..6bb83229b568 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
index 00162b94b0a8..e2e05c94f8ed 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index c97d9f91e1ef..eb63c621a9a4 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 20a8f6f9d088..da1c5c5cebc0 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
index 4d27ed8f58a1..1352957ba7d9 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Banana.cs
index 83737b32ed0d..b1a974648b90 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
index 8a4e8157fdc9..129c725f3ad3 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
index ed964f1dea99..646a24850fab 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Category.cs
index adfb6bb5076a..9428697a62bc 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
index eafd95906774..3782731ad18f 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 2f4b08d39f90..46448cd6084a 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 4148a0a4efe9..60afe853895b 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
index 0d9208ff5c4e..e0e0c98a773c 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
index 379d700af3f1..d0290d43113e 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
index c5b98a8acf8b..6b4568ab3225 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -201,7 +201,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/File.cs
index 978be6bf3452..795846b7c8e3 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c3596b4f7d79..04a0d237ccf1 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Foo.cs
index ebfbcac41665..9c73bd652db4 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 07043466e6a3..fd03617ed923 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
index 36ec7c7b26eb..92d5f91c29c3 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
index 42999757b8fa..784b5dc9af79 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
index 3322eb6f7e15..c9077bcb304a 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index a1263c37991a..dd0923639f7f 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index b0087e834c23..f6248cd06db8 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/List.cs
index 55083fed4563..c88f88c56abf 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index c98cd6b621e8..87f641bef11c 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
index 97bb8da7ad8a..951533a3e5a4 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 1a9b032ad804..c78165a70a1c 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index a644a5c3610f..8f9499a29e1d 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
index def0526bc48f..22bc58e809f4 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 5309a1772be0..23e842d9ff6a 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
index 3bc3896d56ff..c8d4e7d606a7 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
index 4073dbdb33e1..75f0c7edf6cc 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
index 8fc27e9fd8a5..75c71d412d83 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Name.cs
index 7f925e162542..40b9dc332552 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
index e31d9a77da8b..4e8a345d148f 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index b95f5fdcd5f3..aadb184abe88 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
index 2c65bf4c6c90..d680ec1c8ca9 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index f660f8b075be..6517e80cc973 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Order.cs
index 5fe551909fc4..08a648bb6ce7 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Order.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3fcb5458c381..6c64e64ba940 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Pet.cs
index 58d614666577..5765b5dd4290 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Pet.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index e91a9b116ec8..d1c286b8a4ef 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
index f82558027777..c4d05a7678b9 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -618,7 +618,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Result.cs
index d2ca3e9ac752..207fdeb6b9a2 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Return.cs
index 7d3365117205..07cc2b095b7b 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 821bafb5c74b..a69fa50a852d 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index e399e3ef9755..068d6270fe9e 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ebbf47e9c5f1..88c1bbf92490 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Tag.cs
index ef8ec55b20d0..107b07e38baf 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index fbdb0cd4a585..9be93e830da8 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index db4b142b687a..214a5b29a17b 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
index 91b0e0dfec84..2322e3b3cfb6 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -91,7 +91,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 3852ce1829df..a760f8d9ca06 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
index a7c1f97f6c8b..4f754172a639 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/User.cs
index 4ffb503161f7..aaf4092782ab 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Whale.cs
index 087642453d9b..5b5788907f9a 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
index 1f3158514d78..3fc95eeebf2a 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 262803184890..fc8c07b8e164 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs
index 68e6556fe628..b18c293835f7 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 8e4f68052139..127001f2b83f 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 18942823ef58..bf0e4e9bdcc5 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -195,7 +195,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs
index ca288e27e247..f6b242de1261 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -100,7 +100,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs
index 429966bbadbd..416750262075 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs
index beb6f775284d..95c0370d683f 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs
index bd54b3a2f52e..dd0e6f3e1072 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 4c069dc4ce82..105058141730 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index e8675a5a80a1..c0d5a75cd5ba 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs
index 43d194bb8b48..0225bed3c4f3 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs
index 2d6ae93660d9..05c1b9d6bb9c 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs
index 3d0a61033423..3279bfa089e7 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs
index 1ebe60f765ac..9e6b7504defb 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs
index 8fd8c1a51c41..8b18172f4fe1 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -163,7 +163,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs
index edd7f8dacb8b..b84366ca5875 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs
@@ -91,7 +91,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs
index 69e62afafe0c..9c8c7e8867f2 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index f1bad4d77735..e50bd7be664c 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs
index 8bb1b45865ba..32ca88b4ba2a 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 545fa73801f7..e0959bac1663 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index f731dd97b377..387754a117f1 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs
index 7f00e7b6b074..a612d22c6da2 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs
index 1bb43e6a8ee3..88885587ba62 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -84,7 +84,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs
index c8f09af033bd..d0518894c929 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -230,7 +230,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs
index 915278e2837c..24b0e71d7063 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -686,7 +686,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 87ed595f4a42..d021c1a06c0e 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs
index 41c218eaf072..b797c30e9856 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 11f2f7e2ebb7..0625b546c919 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs
index d6a71b2f68e6..b6918e158aa7 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 23310da4d01b..095432b6acd5 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs
index d5e6ef21ec27..524db225d229 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -485,114 +485,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -638,13 +638,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs
index 1cb37dc50b07..a4308c32d8b6 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs
index 13e9d1a5b6bf..d561a09a3804 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs
index 87badf71a4a9..59c8e02abb38 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -102,7 +102,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 001d612fc862..3eed79308214 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -84,7 +84,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 7dfecca3e4c2..c4efe268aeaa 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index 68c52ea737b4..b5a27da55cdd 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index c1cb9bc77c58..e3efc7dd5bb2 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -209,7 +209,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 5b6eed7047ce..e52e9a1a001f 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -77,7 +77,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs
index 64f7d9f90a6c..33f524131799 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index 4113e1c396ec..37c9f514e77a 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs
index 8dae459101ba..3a7ee353247d 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs
@@ -102,7 +102,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -112,7 +112,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs
index 03fef3b9ce60..7153674bfcee 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs
@@ -196,7 +196,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 18da3c77dd48..ed4dfe88eef1 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index f2ba03f1e0d4..78e4de989031 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -135,7 +135,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 9d674926e216..ed5145de010f 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 1a42741423ae..6811c075b9ca 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -132,7 +132,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index a509a5ff65ef..36b610c40036 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs
index f036240b579b..26efa752a2a8 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs
index e4ae282ec9b6..e57fb5119e68 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs
index d0bd57ad9e25..473d5ab1b8bd 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs
index 5ed720c3ccc4..c80eb6ebabbc 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs
@@ -164,7 +164,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 0c5df34a03d3..92db35933844 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs
index d8f280bd09c8..fbb77b864ef8 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -258,7 +258,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 09d2f81739a0..a68f5745d461 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs
index 765b17c09b94..267ac32bcb43 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs
index 9a7e8b24d204..8b315295c063 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index 978db5f11c6e..b381ed067450 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs
index be2cec490d8f..29000bb7adad 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs
index 1d24837d0117..3b714c322a27 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs
@@ -245,7 +245,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3eac7fb0efdf..7f9b2c097b91 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs
index 1607391d0075..4ea8d65be836 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs
@@ -231,7 +231,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs
index e5c2b80f4295..99978f33879e 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 1caaf6f6b92c..c5c884525043 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs
index 52b8cdfb1355..8d9a23c043bd 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 4596a6492745..591fe6abde97 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 8978d99739e1..259cafd3ed88 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs
index 5c1539bc201d..dfb0a1c64797 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1698,7 +1698,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs
index 33001f356a9b..0d7325a10e96 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs
index 86dbc4c2a190..e39fbf85010d 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs
@@ -116,7 +116,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 428fb58213c1..d4488fa657e9 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 8d965d718002..181c17a16cee 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index f8f7b31fde34..1ee8c0944c08 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs
index 76cdea3c0f13..23abcc3c4eb2 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs
index b014ebce7804..b42cb4fea949 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index ab53a15de52d..95fd9f19ca5a 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 31e83cc8e021..58738425c74d 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs
index 781119dc84e7..b6bd9fb06e40 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs
index f12bda6458a9..d2e8171103be 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 21e6e3486671..cd1413cf832e 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index d58357a22252..f36b33493e94 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs
index 927eb828c42c..6f093288a67d 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -149,7 +149,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -159,7 +159,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index b214297afab7..eca952b8d177 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs
index 64f9ac9c690b..5308a3f6befa 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs
@@ -116,7 +116,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs
index 039a2351c3f7..72190dd711ec 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs
@@ -102,7 +102,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -112,7 +112,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs
index e2fc8b97c357..4bc6ca701e71 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs
index b3fe51551553..8f0a63079211 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs
@@ -263,7 +263,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs
index 2fad1c319e4b..26cbad6318d8 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs
@@ -107,7 +107,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs
index 31b6a8d4d271..6fe7ebd5a7b4 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs
@@ -171,7 +171,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index e4137d8207e7..0e0944558e5d 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -148,7 +148,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Apple.cs
index f013ab58aff2..f985f250f712 100644
--- a/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Apple.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Banana.cs
index d2e3592a7114..b1b959afea24 100644
--- a/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Banana.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
index 3bb11c348e51..ba9946bc000b 100644
--- a/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -122,7 +122,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Orange.cs b/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Orange.cs
index 8895e46f2556..cde52f9eeab0 100644
--- a/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Orange.cs
+++ b/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Model/Orange.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index 0baba23ccf52..f51e85f459e9 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 38e288cbbe85..852840c03144 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 8b63e560e3c3..78fd02d9e8fd 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index 2407c49d6e87..b2d1a75913d7 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index af6d432b7f9f..dc2f82b08fea 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index e9c5013017fa..6bb83229b568 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 00162b94b0a8..e2e05c94f8ed 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index c97d9f91e1ef..eb63c621a9a4 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 20a8f6f9d088..da1c5c5cebc0 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 4d27ed8f58a1..1352957ba7d9 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index 83737b32ed0d..b1a974648b90 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index 8a4e8157fdc9..129c725f3ad3 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index ed964f1dea99..646a24850fab 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs
index adfb6bb5076a..9428697a62bc 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index eafd95906774..3782731ad18f 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 2f4b08d39f90..46448cd6084a 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 4148a0a4efe9..60afe853895b 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index 0d9208ff5c4e..e0e0c98a773c 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index cd2dcaa56797..9fa60dc4ea9d 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -228,7 +228,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index 92ecefeb9edd..4885e2fd5b9e 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -684,7 +684,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/File.cs
index 978be6bf3452..795846b7c8e3 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c3596b4f7d79..04a0d237ccf1 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index ebfbcac41665..9c73bd652db4 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 07043466e6a3..fd03617ed923 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 36ec7c7b26eb..92d5f91c29c3 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
index 42999757b8fa..784b5dc9af79 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
index 3322eb6f7e15..c9077bcb304a 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index a1263c37991a..dd0923639f7f 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index 090aa1e836aa..06ca21d289c8 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/List.cs
index 55083fed4563..c88f88c56abf 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index c98cd6b621e8..87f641bef11c 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index b5299c925ca4..368d85aace86 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -194,7 +194,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 1a9b032ad804..c78165a70a1c 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index a644a5c3610f..8f9499a29e1d 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index def0526bc48f..22bc58e809f4 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 5309a1772be0..23e842d9ff6a 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 3bc3896d56ff..c8d4e7d606a7 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index 4073dbdb33e1..75f0c7edf6cc 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 8fc27e9fd8a5..75c71d412d83 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 7f925e162542..40b9dc332552 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index e31d9a77da8b..4e8a345d148f 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index b95f5fdcd5f3..aadb184abe88 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index 2c65bf4c6c90..d680ec1c8ca9 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index f660f8b075be..6517e80cc973 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 1fa14c72cc2f..7a44d1816288 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -243,7 +243,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3fcb5458c381..6c64e64ba940 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index f3b9599a1325..afcb52da70b3 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -229,7 +229,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index e91a9b116ec8..d1c286b8a4ef 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index b6e1fd992a57..559718eef568 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1696,7 +1696,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Result.cs
index d2ca3e9ac752..207fdeb6b9a2 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs
index 7d3365117205..07cc2b095b7b 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 821bafb5c74b..a69fa50a852d 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index e399e3ef9755..068d6270fe9e 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ebbf47e9c5f1..88c1bbf92490 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index ef8ec55b20d0..107b07e38baf 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index fbdb0cd4a585..9be93e830da8 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index db4b142b687a..214a5b29a17b 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
index 3812a5f24758..2b4582eed5a3 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -157,7 +157,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 3852ce1829df..a760f8d9ca06 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
index a7c1f97f6c8b..4f754172a639 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/User.cs
index 4ffb503161f7..aaf4092782ab 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index 087642453d9b..5b5788907f9a 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index c2944781b24a..b345c0cd90dc 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -169,7 +169,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 959d2b03efe1..baaf025cdf9c 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -146,7 +146,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs
index 46121c8de25f..cf7f68a295a7 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 5beaf95a3b55..5b3cc712de8b 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index b5322aa98c71..22a14542e350 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -196,7 +196,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs
index a71f0e5513d5..8131847e5896 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs
@@ -91,7 +91,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -101,7 +101,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs
index ccd192b48a91..ffef8e4c1e88 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs
index 43c476af80c8..765c0ce4833c 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs
index 0a0d2c56ffe1..931572f0dd29 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 0a84f33c9a4c..cd749ab1e3ac 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 26752a0cd36a..b0cc38229098 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs
index 944aa9287a73..b5dc90bd8462 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs
index 572e40e82582..34fd1bd73ac1 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs
index bd71081f4354..f483a58269d9 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs
index b291a9e0675e..bb5a4a24d1d8 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs
index 0aff545dd56c..8ee757ad4d93 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -164,7 +164,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs
index a0cddb6d5d49..e15bd27efc2c 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs
@@ -92,7 +92,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs
index 1c0e9bb09aaf..297907a07938 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index a45a9e372eaf..15c826f538ca 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs
index 56be838031d7..3ab0184bfee5 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index a7a6859eb792..088bd36f7813 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 037467af4fd6..de5675e6e69f 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs
index 77792593add9..679e9cae14e7 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs
index bf2eabddedc5..735180ecd837 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -85,7 +85,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs
index 58a45a6a87cb..6b921e7c3a13 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -231,7 +231,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs
index 8f217f08d673..fb6bed674407 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -687,7 +687,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index c713c15e8e75..fe254376caf2 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/File.cs
index d63a071c30ae..d8d27797c621 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/File.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 667548469483..8531aa1826de 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs
index 189b130ccc4d..eea687ce11b9 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index c8c5fa2a5b55..1135e0e3f1e2 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs
index 904cfb7c2d27..dd27824ed852 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -486,114 +486,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -639,13 +639,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs
index 5e9fa4564a89..faa29c9f5d95 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs
index 40a9aaf3e761..055e99668c60 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs
index 3781db9127c1..04c8c81b09cb 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -103,7 +103,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index ae9897dd949a..6d5ab52e2a83 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -85,7 +85,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 267a9bd7253d..8b4ec708d844 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index eb10f70fc159..fd5a1217a5c5 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index a5a551d58f03..1f83a7746e58 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -210,7 +210,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 18af0f861459..3bb832b139ee 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/List.cs
index 664fa067d24c..9dfd448b7e09 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/List.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index fbd2d2eb5273..2cf4c582f440 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs
index 6fd97f187117..1f96c8cf478e 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs
@@ -103,7 +103,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -113,7 +113,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs
index 15717778c839..654138d859fe 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs
@@ -197,7 +197,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index e6d8bd647e7a..7c59091d976b 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index b88a7e3c06af..f133840f6eb2 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -136,7 +136,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 0cf6230eb6bf..90b0d2773ad3 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 056b2b994649..8ef84d0e9496 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index e345c816ef94..91d296ad1073 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs
index 2548f40af76e..61592492cbbb 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs
index bac80386c438..d4bc1846a6d5 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs
index 3058a0066248..ab3f01486445 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs
index 3ce1f23d1746..dd4a4198792f 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs
@@ -165,7 +165,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 3db174a72bf7..429d00bbd1d6 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs
index 151ae9462421..0624c8bcd173 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -259,7 +259,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 7aa2022a3dbe..ad76f0195476 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs
index b094f730ebc4..41885b4ce7d6 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs
index d8a6197c7490..441aa6537a89 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index a6c1d895cfda..2ba29dccf002 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -134,7 +134,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs
index 8bca9c113496..a82cef00ef30 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs
index 969537d113a7..ef0f880c2f26 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs
@@ -246,7 +246,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs
index 5e1a645aa922..aa2e44423b3e 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs
index 71c2b601e315..adb4cc86726e 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs
@@ -232,7 +232,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs
index b3abfe311cca..40bdd7cdc98b 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index e0baef9347bc..bb23a0e706e9 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -118,7 +118,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs
index 850de679ebf5..409b7ef3afc3 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 03646d05416b..c8b23b20ef78 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index f1ba87a2635c..1cf1d284f733 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs
index 4a5e527df630..bc256be1ea79 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1699,7 +1699,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs
index 7724cc47e7e3..a3fbe08251a0 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs
@@ -118,7 +118,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs
index e0bbb6a90515..4cd64f8cfbd0 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index c227978f4c94..4c549d0b0c13 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 95e96c442bb9..eed2b499ad8a 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 538857e10d49..9ad7288dee19 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs
index 92a7d9bf8462..7759e1e17d39 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 78ba8e07009a..dcd8ac1b9a2b 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index f8350930f14a..d6d75a35d578 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 964f5b3ed00e..68d941a3d0dd 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs
index 0e3972e37a16..914fb011b3b6 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs
index 56424996d5c0..5f1fd6c6fe82 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 1e54eafcfa2b..d14f40675ef0 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 64b45c2a1d34..bd9abfb5330b 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs
index 90d78d2e066f..352f06d49187 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -150,7 +150,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -160,7 +160,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index bb87cf541324..86acdbef9c28 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs
index 4205752aa4d2..f4eec4a5d5b3 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs
index 399994e28dc2..f70ae70ab310 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs
@@ -103,7 +103,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -113,7 +113,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 1892a822d865..538fede8f102 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/User.cs
index 04daff1ed7be..3ba80694ac78 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/User.cs
@@ -264,7 +264,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs
index 29bde9dd1ac8..6ba6b5f02465 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs
@@ -108,7 +108,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs
index f60c1b215254..8c95f7355802 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs
@@ -172,7 +172,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index f0e86093b153..b7afd8a130cd 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -149,7 +149,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net10/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs b/samples/client/petstore/csharp/generichost/net10/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
index e55c4400d994..b0999ebf8aa0 100644
--- a/samples/client/petstore/csharp/generichost/net10/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net10/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Model/Person.cs b/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Model/Person.cs
index d2361b98b378..942e20a5cb37 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Model/Person.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Model/Person.cs
@@ -104,7 +104,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -114,7 +114,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
index 4fe8ad9cc6dc..6ba2ef68e710 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
index 4f1337d74655..0297762ff18d 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
index 33ae6928a6bb..1177863c285b 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -107,7 +107,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
index 8b3c93cc0c0e..7b69c365fea9 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
index 2c09da6fbd14..88405057c9d5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
index b247159127c6..62d7634477a2 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
@@ -106,7 +106,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Activity.cs
index 404476d906b0..b16edf9585ec 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 46ae0e3f391d..791135466d90 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index e01cfeffeb0d..32d404f7517b 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Animal.cs
index 1f0daf2c9e58..b47f118fa92d 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
index 5fd2aa296926..bfceb53e9c48 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Apple.cs
index ef8268a90a59..91ac5a77261a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
index 4938fc5a2e5b..d025c754f594 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index d085ea5e2d2c..970a9992550b 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index dc3b303411ef..95a13de67b5a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
index eaf99dd9f801..04441ef4f8dc 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Banana.cs
index 32eea508145d..2259033dfd28 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
index 42d1bc50f756..1049c3908fb3 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
index 94ce156e0bf6..ae87e9aa15bd 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Category.cs
index 062bc4656542..278a9393a1c8 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
index 15973b9e79fa..4bfeb403a9af 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 84207ba12890..2b49d4004c96 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 747fbc7166f1..d3e470b96e7f 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
index 28b81cba6536..1e0d226457ce 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
index c584e4cd38cc..54304bf3d00a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
index 82491a31c01f..ea0fa7c110db 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -201,7 +201,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/File.cs
index 028476ef05b2..1db7613177ff 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index e7f69a24ef3d..01b95e690f2a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Foo.cs
index 8620b135a5d6..fbac0b2823ca 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index d0aa9bc4699a..078883656dba 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
index 27c50ce1bbe3..165f723307f4 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
index 8ad0d64c1be5..ba7eb93c2ec2 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
index 4b122a792d91..02322bad0ce5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index ffd2310b3213..0182e92ea13d 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index 154e205c9166..96fa99ca40b1 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/List.cs
index 2f275baa700f..c11932926f79 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index ab45fc36b6c7..22e94ce9d28e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
index cba96541fc88..8b78f997902e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index bb4959ca5175..54aac5d896e1 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index b8fc88212401..c34b0aeb80fd 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 706d7fc6b64c..d2e512b7c931 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 3c3c09b4f2f5..4e655fdffe1f 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
index 121a21a30b23..0e8b992439e4 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
index aceb8d425b94..bf7af7d752d9 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
index 2d1e29add011..ed31adedc185 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Name.cs
index 4517587d378c..faee8445cbd4 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
index f32957f8dc40..4b1de3bbf890 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 450d192600cb..876ec6812878 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
index 1ef25662ecf5..81c3755c3a0f 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index e71b7f7939c3..1416a7d02013 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Order.cs
index c1c0b66adb69..404e3ab0c062 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Order.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
index c455c6d87241..0d78e7d0dcd5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Pet.cs
index 47d94d67468a..c9e8080d9a8b 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Pet.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 40b6be4e4165..d759665cf4ab 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
index 545dcf72dd65..b6182e3bd1a4 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -618,7 +618,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Result.cs
index b4d4a5929709..fb9df5a6ecef 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Return.cs
index 7a33ca9ddb15..1422ed929401 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 8a95a1148df5..3c499e2d5c1e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 2b94fa2026fd..c58167c8073e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ad59ab442459..9a1d720f4388 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Tag.cs
index e2213d2d75e1..50857c190256 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bae68ea3d331..3a4b6246362c 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 272a27134f49..c77826536550 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
index 91b0e0dfec84..2322e3b3cfb6 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -91,7 +91,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 9c44f845a1ac..c44e3d4fcc62 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
index d8f5f794a076..9f3a467c19f5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/User.cs
index f0bc20b7756d..652b50ab6da7 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Whale.cs
index e43fef0983cd..109770eb7140 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
index 803767b26def..bc1e24e52488 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 9a6741806bf8..77cdae47bfee 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Apple.cs
index 4fe8ad9cc6dc..6ba2ef68e710 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Apple.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Banana.cs
index 4f1337d74655..0297762ff18d 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
index a5a0596e62bd..0d2df9da3d80 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -120,7 +120,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Orange.cs b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Orange.cs
index 60af42ed154c..831a1f655fb1 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Orange.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Model/Orange.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index 404476d906b0..b16edf9585ec 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 46ae0e3f391d..791135466d90 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index e01cfeffeb0d..32d404f7517b 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index 1f0daf2c9e58..b47f118fa92d 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index 5fd2aa296926..bfceb53e9c48 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index ef8268a90a59..91ac5a77261a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 4938fc5a2e5b..d025c754f594 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index d085ea5e2d2c..970a9992550b 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index dc3b303411ef..95a13de67b5a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index eaf99dd9f801..04441ef4f8dc 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index 32eea508145d..2259033dfd28 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index 42d1bc50f756..1049c3908fb3 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index 94ce156e0bf6..ae87e9aa15bd 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Category.cs
index 062bc4656542..278a9393a1c8 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 15973b9e79fa..4bfeb403a9af 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 84207ba12890..2b49d4004c96 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 747fbc7166f1..d3e470b96e7f 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index 28b81cba6536..1e0d226457ce 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index a1790a1a6ea3..07139226b993 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -228,7 +228,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index a5e46b184b61..55fbc1964ebf 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -684,7 +684,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/File.cs
index 028476ef05b2..1db7613177ff 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index e7f69a24ef3d..01b95e690f2a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 8620b135a5d6..fbac0b2823ca 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index d0aa9bc4699a..078883656dba 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 27c50ce1bbe3..165f723307f4 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
index 8ad0d64c1be5..ba7eb93c2ec2 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
index 4b122a792d91..02322bad0ce5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index ffd2310b3213..0182e92ea13d 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index 154e205c9166..96fa99ca40b1 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/List.cs
index 2f275baa700f..c11932926f79 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index ab45fc36b6c7..22e94ce9d28e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index 888d9392b1f6..d532f0f9c93a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -194,7 +194,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index bb4959ca5175..54aac5d896e1 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index b8fc88212401..c34b0aeb80fd 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 706d7fc6b64c..d2e512b7c931 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 3c3c09b4f2f5..4e655fdffe1f 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 121a21a30b23..0e8b992439e4 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index aceb8d425b94..bf7af7d752d9 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 2d1e29add011..ed31adedc185 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 4517587d378c..faee8445cbd4 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index f32957f8dc40..4b1de3bbf890 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 450d192600cb..876ec6812878 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index 1ef25662ecf5..81c3755c3a0f 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index e71b7f7939c3..1416a7d02013 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 42136304b77a..a9aad4e98bc4 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -243,7 +243,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index c455c6d87241..0d78e7d0dcd5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index b11ba88083fc..f4ce1f31fb1a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -229,7 +229,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 40b6be4e4165..d759665cf4ab 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index 3aa2cc985648..e6715816b6ca 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1696,7 +1696,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Result.cs
index b4d4a5929709..fb9df5a6ecef 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Return.cs
index 7a33ca9ddb15..1422ed929401 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 8a95a1148df5..3c499e2d5c1e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 2b94fa2026fd..c58167c8073e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ad59ab442459..9a1d720f4388 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index e2213d2d75e1..50857c190256 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bae68ea3d331..3a4b6246362c 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 272a27134f49..c77826536550 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
index 3812a5f24758..2b4582eed5a3 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -157,7 +157,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 9c44f845a1ac..c44e3d4fcc62 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
index d8f5f794a076..9f3a467c19f5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/User.cs
index f0bc20b7756d..652b50ab6da7 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index e43fef0983cd..109770eb7140 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index d501d9990668..43e1a5acdffb 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -169,7 +169,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 55b029c7fd90..a5e10fb39370 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -146,7 +146,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs b/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
index 474f9cf9325d..e38f0e2bcec6 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Model/Person.cs b/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Model/Person.cs
index d2361b98b378..942e20a5cb37 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Model/Person.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Model/Person.cs
@@ -104,7 +104,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -114,7 +114,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
index 4fe8ad9cc6dc..6ba2ef68e710 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
index 4f1337d74655..0297762ff18d 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
index 33ae6928a6bb..1177863c285b 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -107,7 +107,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
index 8b3c93cc0c0e..7b69c365fea9 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
index 2c09da6fbd14..88405057c9d5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
@@ -79,7 +79,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
index b247159127c6..62d7634477a2 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
@@ -106,7 +106,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Activity.cs
index 404476d906b0..b16edf9585ec 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 46ae0e3f391d..791135466d90 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index e01cfeffeb0d..32d404f7517b 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Animal.cs
index 1f0daf2c9e58..b47f118fa92d 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
index 5fd2aa296926..bfceb53e9c48 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Apple.cs
index ef8268a90a59..91ac5a77261a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
index 4938fc5a2e5b..d025c754f594 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index d085ea5e2d2c..970a9992550b 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index dc3b303411ef..95a13de67b5a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
index eaf99dd9f801..04441ef4f8dc 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Banana.cs
index 32eea508145d..2259033dfd28 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
index 42d1bc50f756..1049c3908fb3 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
index 94ce156e0bf6..ae87e9aa15bd 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Category.cs
index 062bc4656542..278a9393a1c8 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
index 15973b9e79fa..4bfeb403a9af 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 84207ba12890..2b49d4004c96 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 747fbc7166f1..d3e470b96e7f 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
index 28b81cba6536..1e0d226457ce 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
index c584e4cd38cc..54304bf3d00a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
index 82491a31c01f..ea0fa7c110db 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -201,7 +201,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/File.cs
index 028476ef05b2..1db7613177ff 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index e7f69a24ef3d..01b95e690f2a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Foo.cs
index 8620b135a5d6..fbac0b2823ca 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index d0aa9bc4699a..078883656dba 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
index 27c50ce1bbe3..165f723307f4 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
index 8ad0d64c1be5..ba7eb93c2ec2 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
index 4b122a792d91..02322bad0ce5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index ffd2310b3213..0182e92ea13d 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index 154e205c9166..96fa99ca40b1 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/List.cs
index 2f275baa700f..c11932926f79 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index ab45fc36b6c7..22e94ce9d28e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
index cba96541fc88..8b78f997902e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index bb4959ca5175..54aac5d896e1 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index b8fc88212401..c34b0aeb80fd 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 706d7fc6b64c..d2e512b7c931 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 3c3c09b4f2f5..4e655fdffe1f 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
index 121a21a30b23..0e8b992439e4 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
index aceb8d425b94..bf7af7d752d9 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
index 2d1e29add011..ed31adedc185 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Name.cs
index 4517587d378c..faee8445cbd4 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
index f32957f8dc40..4b1de3bbf890 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 450d192600cb..876ec6812878 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
index 1ef25662ecf5..81c3755c3a0f 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index e71b7f7939c3..1416a7d02013 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Order.cs
index c1c0b66adb69..404e3ab0c062 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Order.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
index c455c6d87241..0d78e7d0dcd5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Pet.cs
index 47d94d67468a..c9e8080d9a8b 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Pet.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 40b6be4e4165..d759665cf4ab 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
index 545dcf72dd65..b6182e3bd1a4 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -618,7 +618,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Result.cs
index b4d4a5929709..fb9df5a6ecef 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Return.cs
index 7a33ca9ddb15..1422ed929401 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 8a95a1148df5..3c499e2d5c1e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 2b94fa2026fd..c58167c8073e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ad59ab442459..9a1d720f4388 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Tag.cs
index e2213d2d75e1..50857c190256 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bae68ea3d331..3a4b6246362c 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 272a27134f49..c77826536550 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
index 91b0e0dfec84..2322e3b3cfb6 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -91,7 +91,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 9c44f845a1ac..c44e3d4fcc62 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
index d8f5f794a076..9f3a467c19f5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/User.cs
index f0bc20b7756d..652b50ab6da7 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Whale.cs
index e43fef0983cd..109770eb7140 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
index 803767b26def..bc1e24e52488 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 9a6741806bf8..77cdae47bfee 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Apple.cs
index 4fe8ad9cc6dc..6ba2ef68e710 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Apple.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Banana.cs
index 4f1337d74655..0297762ff18d 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
index a5a0596e62bd..0d2df9da3d80 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -120,7 +120,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Orange.cs b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Orange.cs
index 60af42ed154c..831a1f655fb1 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Orange.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Model/Orange.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index 404476d906b0..b16edf9585ec 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 46ae0e3f391d..791135466d90 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index e01cfeffeb0d..32d404f7517b 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index 1f0daf2c9e58..b47f118fa92d 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index 5fd2aa296926..bfceb53e9c48 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index ef8268a90a59..91ac5a77261a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 4938fc5a2e5b..d025c754f594 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index d085ea5e2d2c..970a9992550b 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index dc3b303411ef..95a13de67b5a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index eaf99dd9f801..04441ef4f8dc 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index 32eea508145d..2259033dfd28 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index 42d1bc50f756..1049c3908fb3 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index 94ce156e0bf6..ae87e9aa15bd 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Category.cs
index 062bc4656542..278a9393a1c8 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 15973b9e79fa..4bfeb403a9af 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 84207ba12890..2b49d4004c96 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 747fbc7166f1..d3e470b96e7f 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index 28b81cba6536..1e0d226457ce 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index a1790a1a6ea3..07139226b993 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -228,7 +228,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index a5e46b184b61..55fbc1964ebf 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -684,7 +684,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/File.cs
index 028476ef05b2..1db7613177ff 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index e7f69a24ef3d..01b95e690f2a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 8620b135a5d6..fbac0b2823ca 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index d0aa9bc4699a..078883656dba 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 27c50ce1bbe3..165f723307f4 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
index 8ad0d64c1be5..ba7eb93c2ec2 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
index 4b122a792d91..02322bad0ce5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index ffd2310b3213..0182e92ea13d 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index 154e205c9166..96fa99ca40b1 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/List.cs
index 2f275baa700f..c11932926f79 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index ab45fc36b6c7..22e94ce9d28e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index 888d9392b1f6..d532f0f9c93a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -194,7 +194,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index bb4959ca5175..54aac5d896e1 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index b8fc88212401..c34b0aeb80fd 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 706d7fc6b64c..d2e512b7c931 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 3c3c09b4f2f5..4e655fdffe1f 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 121a21a30b23..0e8b992439e4 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index aceb8d425b94..bf7af7d752d9 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 2d1e29add011..ed31adedc185 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 4517587d378c..faee8445cbd4 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index f32957f8dc40..4b1de3bbf890 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 450d192600cb..876ec6812878 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index 1ef25662ecf5..81c3755c3a0f 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index e71b7f7939c3..1416a7d02013 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 42136304b77a..a9aad4e98bc4 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -243,7 +243,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index c455c6d87241..0d78e7d0dcd5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index b11ba88083fc..f4ce1f31fb1a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -229,7 +229,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 40b6be4e4165..d759665cf4ab 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index 3aa2cc985648..e6715816b6ca 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1696,7 +1696,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Result.cs
index b4d4a5929709..fb9df5a6ecef 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Return.cs
index 7a33ca9ddb15..1422ed929401 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 8a95a1148df5..3c499e2d5c1e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 2b94fa2026fd..c58167c8073e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ad59ab442459..9a1d720f4388 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index e2213d2d75e1..50857c190256 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bae68ea3d331..3a4b6246362c 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 272a27134f49..c77826536550 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
index 3812a5f24758..2b4582eed5a3 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -157,7 +157,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 9c44f845a1ac..c44e3d4fcc62 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
index d8f5f794a076..9f3a467c19f5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/User.cs
index f0bc20b7756d..652b50ab6da7 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index e43fef0983cd..109770eb7140 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index d501d9990668..43e1a5acdffb 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -169,7 +169,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 55b029c7fd90..a5e10fb39370 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -146,7 +146,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs b/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
index 474f9cf9325d..e38f0e2bcec6 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Model/Person.cs b/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Model/Person.cs
index a8f07fd13d7a..4373e60686d9 100644
--- a/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Model/Person.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Model/Person.cs
@@ -106,7 +106,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -116,7 +116,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
index f013ab58aff2..f985f250f712 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
index d2e3592a7114..b1b959afea24 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
index d283da3cd5f9..f5af2e0caaf1 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -109,7 +109,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
index 8cfcda99a1d7..0754094c6901 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
index 2be6e1b0501c..893a8623dc4f 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
index ebcf62ab1443..55d4d2ba7126 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
@@ -108,7 +108,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Activity.cs
index 0baba23ccf52..f51e85f459e9 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 38e288cbbe85..852840c03144 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 8b63e560e3c3..78fd02d9e8fd 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Animal.cs
index 2407c49d6e87..b2d1a75913d7 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
index af6d432b7f9f..dc2f82b08fea 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Apple.cs
index e9c5013017fa..6bb83229b568 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
index 00162b94b0a8..e2e05c94f8ed 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index c97d9f91e1ef..eb63c621a9a4 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 20a8f6f9d088..da1c5c5cebc0 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
index 4d27ed8f58a1..1352957ba7d9 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Banana.cs
index 83737b32ed0d..b1a974648b90 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
index 8a4e8157fdc9..129c725f3ad3 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
index ed964f1dea99..646a24850fab 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Category.cs
index adfb6bb5076a..9428697a62bc 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
index eafd95906774..3782731ad18f 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 2f4b08d39f90..46448cd6084a 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 4148a0a4efe9..60afe853895b 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
index 0d9208ff5c4e..e0e0c98a773c 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
index 379d700af3f1..d0290d43113e 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
index c5b98a8acf8b..6b4568ab3225 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -201,7 +201,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/File.cs
index 978be6bf3452..795846b7c8e3 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c3596b4f7d79..04a0d237ccf1 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Foo.cs
index ebfbcac41665..9c73bd652db4 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 07043466e6a3..fd03617ed923 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
index 36ec7c7b26eb..92d5f91c29c3 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
index 42999757b8fa..784b5dc9af79 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
index 3322eb6f7e15..c9077bcb304a 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index a1263c37991a..dd0923639f7f 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index b0087e834c23..f6248cd06db8 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/List.cs
index 55083fed4563..c88f88c56abf 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index c98cd6b621e8..87f641bef11c 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
index 97bb8da7ad8a..951533a3e5a4 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 1a9b032ad804..c78165a70a1c 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index a644a5c3610f..8f9499a29e1d 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
index def0526bc48f..22bc58e809f4 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 5309a1772be0..23e842d9ff6a 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
index 3bc3896d56ff..c8d4e7d606a7 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
index 4073dbdb33e1..75f0c7edf6cc 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
index 8fc27e9fd8a5..75c71d412d83 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Name.cs
index 7f925e162542..40b9dc332552 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
index e31d9a77da8b..4e8a345d148f 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index b95f5fdcd5f3..aadb184abe88 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
index 2c65bf4c6c90..d680ec1c8ca9 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index f660f8b075be..6517e80cc973 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Order.cs
index 5fe551909fc4..08a648bb6ce7 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Order.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3fcb5458c381..6c64e64ba940 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Pet.cs
index 58d614666577..5765b5dd4290 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Pet.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index e91a9b116ec8..d1c286b8a4ef 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
index f82558027777..c4d05a7678b9 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -618,7 +618,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Result.cs
index d2ca3e9ac752..207fdeb6b9a2 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Return.cs
index 7d3365117205..07cc2b095b7b 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 821bafb5c74b..a69fa50a852d 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index e399e3ef9755..068d6270fe9e 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ebbf47e9c5f1..88c1bbf92490 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Tag.cs
index ef8ec55b20d0..107b07e38baf 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index fbdb0cd4a585..9be93e830da8 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index db4b142b687a..214a5b29a17b 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
index 91b0e0dfec84..2322e3b3cfb6 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -91,7 +91,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 3852ce1829df..a760f8d9ca06 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
index a7c1f97f6c8b..4f754172a639 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/User.cs
index 4ffb503161f7..aaf4092782ab 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Whale.cs
index 087642453d9b..5b5788907f9a 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
index 1f3158514d78..3fc95eeebf2a 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 262803184890..fc8c07b8e164 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs
index 68e6556fe628..b18c293835f7 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 8e4f68052139..127001f2b83f 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 18942823ef58..bf0e4e9bdcc5 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -195,7 +195,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs
index ca288e27e247..f6b242de1261 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -100,7 +100,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs
index 429966bbadbd..416750262075 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs
index beb6f775284d..95c0370d683f 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs
index bd54b3a2f52e..dd0e6f3e1072 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 4c069dc4ce82..105058141730 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index e8675a5a80a1..c0d5a75cd5ba 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs
index 43d194bb8b48..0225bed3c4f3 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs
index 2d6ae93660d9..05c1b9d6bb9c 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs
index 3d0a61033423..3279bfa089e7 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs
index 1ebe60f765ac..9e6b7504defb 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs
index 8fd8c1a51c41..8b18172f4fe1 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -163,7 +163,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs
index edd7f8dacb8b..b84366ca5875 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs
@@ -91,7 +91,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs
index 69e62afafe0c..9c8c7e8867f2 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index f1bad4d77735..e50bd7be664c 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs
index 8bb1b45865ba..32ca88b4ba2a 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 545fa73801f7..e0959bac1663 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index f731dd97b377..387754a117f1 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs
index 7f00e7b6b074..a612d22c6da2 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs
index 1bb43e6a8ee3..88885587ba62 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -84,7 +84,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs
index c8f09af033bd..d0518894c929 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -230,7 +230,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs
index 915278e2837c..24b0e71d7063 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -686,7 +686,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 87ed595f4a42..d021c1a06c0e 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs
index 41c218eaf072..b797c30e9856 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 11f2f7e2ebb7..0625b546c919 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs
index d6a71b2f68e6..b6918e158aa7 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 23310da4d01b..095432b6acd5 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs
index d5e6ef21ec27..524db225d229 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -485,114 +485,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -638,13 +638,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs
index 1cb37dc50b07..a4308c32d8b6 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs
index 13e9d1a5b6bf..d561a09a3804 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs
index 87badf71a4a9..59c8e02abb38 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -102,7 +102,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 001d612fc862..3eed79308214 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -84,7 +84,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 7dfecca3e4c2..c4efe268aeaa 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index 68c52ea737b4..b5a27da55cdd 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index c1cb9bc77c58..e3efc7dd5bb2 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -209,7 +209,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 5b6eed7047ce..e52e9a1a001f 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -77,7 +77,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs
index 64f7d9f90a6c..33f524131799 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index 4113e1c396ec..37c9f514e77a 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs
index 8dae459101ba..3a7ee353247d 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs
@@ -102,7 +102,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -112,7 +112,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs
index 03fef3b9ce60..7153674bfcee 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs
@@ -196,7 +196,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 18da3c77dd48..ed4dfe88eef1 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index f2ba03f1e0d4..78e4de989031 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -135,7 +135,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 9d674926e216..ed5145de010f 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 1a42741423ae..6811c075b9ca 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -132,7 +132,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index a509a5ff65ef..36b610c40036 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs
index f036240b579b..26efa752a2a8 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs
index e4ae282ec9b6..e57fb5119e68 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs
index d0bd57ad9e25..473d5ab1b8bd 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs
index 5ed720c3ccc4..c80eb6ebabbc 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs
@@ -164,7 +164,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 0c5df34a03d3..92db35933844 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs
index d8f280bd09c8..fbb77b864ef8 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -258,7 +258,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 09d2f81739a0..a68f5745d461 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs
index 765b17c09b94..267ac32bcb43 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs
index 9a7e8b24d204..8b315295c063 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index 978db5f11c6e..b381ed067450 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs
index be2cec490d8f..29000bb7adad 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs
index 1d24837d0117..3b714c322a27 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs
@@ -245,7 +245,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3eac7fb0efdf..7f9b2c097b91 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs
index 1607391d0075..4ea8d65be836 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs
@@ -231,7 +231,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs
index e5c2b80f4295..99978f33879e 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 1caaf6f6b92c..c5c884525043 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs
index 52b8cdfb1355..8d9a23c043bd 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 4596a6492745..591fe6abde97 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 8978d99739e1..259cafd3ed88 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs
index 5c1539bc201d..dfb0a1c64797 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1698,7 +1698,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs
index 33001f356a9b..0d7325a10e96 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs
index 86dbc4c2a190..e39fbf85010d 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs
@@ -116,7 +116,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 428fb58213c1..d4488fa657e9 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 8d965d718002..181c17a16cee 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index f8f7b31fde34..1ee8c0944c08 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs
index 76cdea3c0f13..23abcc3c4eb2 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs
index b014ebce7804..b42cb4fea949 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index ab53a15de52d..95fd9f19ca5a 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 31e83cc8e021..58738425c74d 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs
index 781119dc84e7..b6bd9fb06e40 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs
index f12bda6458a9..d2e8171103be 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 21e6e3486671..cd1413cf832e 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index d58357a22252..f36b33493e94 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs
index 927eb828c42c..6f093288a67d 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -149,7 +149,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -159,7 +159,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index b214297afab7..eca952b8d177 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs
index 64f9ac9c690b..5308a3f6befa 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs
@@ -116,7 +116,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs
index 039a2351c3f7..72190dd711ec 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs
@@ -102,7 +102,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -112,7 +112,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs
index e2fc8b97c357..4bc6ca701e71 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs
index b3fe51551553..8f0a63079211 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs
@@ -263,7 +263,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs
index 2fad1c319e4b..26cbad6318d8 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs
@@ -107,7 +107,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs
index 31b6a8d4d271..6fe7ebd5a7b4 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs
@@ -171,7 +171,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index e4137d8207e7..0e0944558e5d 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -148,7 +148,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Apple.cs
index f013ab58aff2..f985f250f712 100644
--- a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Apple.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Banana.cs
index d2e3592a7114..b1b959afea24 100644
--- a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Banana.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
index 3bb11c348e51..ba9946bc000b 100644
--- a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -122,7 +122,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Orange.cs b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Orange.cs
index 8895e46f2556..cde52f9eeab0 100644
--- a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Orange.cs
+++ b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Orange.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index 0baba23ccf52..f51e85f459e9 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 38e288cbbe85..852840c03144 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 8b63e560e3c3..78fd02d9e8fd 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index 2407c49d6e87..b2d1a75913d7 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index af6d432b7f9f..dc2f82b08fea 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index e9c5013017fa..6bb83229b568 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 00162b94b0a8..e2e05c94f8ed 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index c97d9f91e1ef..eb63c621a9a4 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 20a8f6f9d088..da1c5c5cebc0 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 4d27ed8f58a1..1352957ba7d9 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index 83737b32ed0d..b1a974648b90 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index 8a4e8157fdc9..129c725f3ad3 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index ed964f1dea99..646a24850fab 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Category.cs
index adfb6bb5076a..9428697a62bc 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index eafd95906774..3782731ad18f 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 2f4b08d39f90..46448cd6084a 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 4148a0a4efe9..60afe853895b 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index 0d9208ff5c4e..e0e0c98a773c 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index cd2dcaa56797..9fa60dc4ea9d 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -228,7 +228,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index 92ecefeb9edd..4885e2fd5b9e 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -684,7 +684,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/File.cs
index 978be6bf3452..795846b7c8e3 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c3596b4f7d79..04a0d237ccf1 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index ebfbcac41665..9c73bd652db4 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 07043466e6a3..fd03617ed923 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 36ec7c7b26eb..92d5f91c29c3 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
index 42999757b8fa..784b5dc9af79 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
index 3322eb6f7e15..c9077bcb304a 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index a1263c37991a..dd0923639f7f 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index b0087e834c23..f6248cd06db8 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/List.cs
index 55083fed4563..c88f88c56abf 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index c98cd6b621e8..87f641bef11c 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index b5299c925ca4..368d85aace86 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -194,7 +194,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 1a9b032ad804..c78165a70a1c 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index a644a5c3610f..8f9499a29e1d 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index def0526bc48f..22bc58e809f4 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 5309a1772be0..23e842d9ff6a 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 3bc3896d56ff..c8d4e7d606a7 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index 4073dbdb33e1..75f0c7edf6cc 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 8fc27e9fd8a5..75c71d412d83 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 7f925e162542..40b9dc332552 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index e31d9a77da8b..4e8a345d148f 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index b95f5fdcd5f3..aadb184abe88 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index 2c65bf4c6c90..d680ec1c8ca9 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index f660f8b075be..6517e80cc973 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 1fa14c72cc2f..7a44d1816288 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -243,7 +243,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3fcb5458c381..6c64e64ba940 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index f3b9599a1325..afcb52da70b3 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -229,7 +229,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index e91a9b116ec8..d1c286b8a4ef 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index b6e1fd992a57..559718eef568 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1696,7 +1696,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Result.cs
index d2ca3e9ac752..207fdeb6b9a2 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Return.cs
index 7d3365117205..07cc2b095b7b 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 821bafb5c74b..a69fa50a852d 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index e399e3ef9755..068d6270fe9e 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ebbf47e9c5f1..88c1bbf92490 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index ef8ec55b20d0..107b07e38baf 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index fbdb0cd4a585..9be93e830da8 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index db4b142b687a..214a5b29a17b 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
index 3812a5f24758..2b4582eed5a3 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -157,7 +157,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 3852ce1829df..a760f8d9ca06 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
index a7c1f97f6c8b..4f754172a639 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/User.cs
index 4ffb503161f7..aaf4092782ab 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index 087642453d9b..5b5788907f9a 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index c2944781b24a..b345c0cd90dc 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -169,7 +169,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 959d2b03efe1..baaf025cdf9c 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -146,7 +146,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs
index 46121c8de25f..cf7f68a295a7 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 5beaf95a3b55..5b3cc712de8b 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index b5322aa98c71..22a14542e350 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -196,7 +196,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs
index a71f0e5513d5..8131847e5896 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs
@@ -91,7 +91,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -101,7 +101,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs
index ccd192b48a91..ffef8e4c1e88 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs
index 43c476af80c8..765c0ce4833c 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs
index 0a0d2c56ffe1..931572f0dd29 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 0a84f33c9a4c..cd749ab1e3ac 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 26752a0cd36a..b0cc38229098 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs
index 944aa9287a73..b5dc90bd8462 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs
index 572e40e82582..34fd1bd73ac1 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs
index bd71081f4354..f483a58269d9 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs
index b291a9e0675e..bb5a4a24d1d8 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs
index 0aff545dd56c..8ee757ad4d93 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -164,7 +164,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs
index a0cddb6d5d49..e15bd27efc2c 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs
@@ -92,7 +92,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs
index 1c0e9bb09aaf..297907a07938 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index a45a9e372eaf..15c826f538ca 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs
index 56be838031d7..3ab0184bfee5 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index a7a6859eb792..088bd36f7813 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 037467af4fd6..de5675e6e69f 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs
index 77792593add9..679e9cae14e7 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs
index bf2eabddedc5..735180ecd837 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -85,7 +85,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs
index 58a45a6a87cb..6b921e7c3a13 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -231,7 +231,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs
index 8f217f08d673..fb6bed674407 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -687,7 +687,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index c713c15e8e75..fe254376caf2 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/File.cs
index d63a071c30ae..d8d27797c621 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/File.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 667548469483..8531aa1826de 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs
index 189b130ccc4d..eea687ce11b9 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index c8c5fa2a5b55..1135e0e3f1e2 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs
index 904cfb7c2d27..dd27824ed852 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -486,114 +486,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -639,13 +639,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs
index 5e9fa4564a89..faa29c9f5d95 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs
index 40a9aaf3e761..055e99668c60 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs
index 3781db9127c1..04c8c81b09cb 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -103,7 +103,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index ae9897dd949a..6d5ab52e2a83 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -85,7 +85,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 267a9bd7253d..8b4ec708d844 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index eb10f70fc159..fd5a1217a5c5 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index a5a551d58f03..1f83a7746e58 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -210,7 +210,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 18af0f861459..3bb832b139ee 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/List.cs
index 664fa067d24c..9dfd448b7e09 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/List.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index fbd2d2eb5273..2cf4c582f440 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs
index 6fd97f187117..1f96c8cf478e 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs
@@ -103,7 +103,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -113,7 +113,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs
index 15717778c839..654138d859fe 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs
@@ -197,7 +197,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index e6d8bd647e7a..7c59091d976b 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index b88a7e3c06af..f133840f6eb2 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -136,7 +136,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 0cf6230eb6bf..90b0d2773ad3 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 056b2b994649..8ef84d0e9496 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index e345c816ef94..91d296ad1073 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs
index 2548f40af76e..61592492cbbb 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs
index bac80386c438..d4bc1846a6d5 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs
index 3058a0066248..ab3f01486445 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs
index 3ce1f23d1746..dd4a4198792f 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs
@@ -165,7 +165,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 3db174a72bf7..429d00bbd1d6 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs
index 151ae9462421..0624c8bcd173 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -259,7 +259,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 7aa2022a3dbe..ad76f0195476 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs
index b094f730ebc4..41885b4ce7d6 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs
index d8a6197c7490..441aa6537a89 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index a6c1d895cfda..2ba29dccf002 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -134,7 +134,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs
index 8bca9c113496..a82cef00ef30 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs
index 969537d113a7..ef0f880c2f26 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs
@@ -246,7 +246,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs
index 5e1a645aa922..aa2e44423b3e 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs
index 71c2b601e315..adb4cc86726e 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs
@@ -232,7 +232,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs
index b3abfe311cca..40bdd7cdc98b 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index e0baef9347bc..bb23a0e706e9 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -118,7 +118,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs
index 850de679ebf5..409b7ef3afc3 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 03646d05416b..c8b23b20ef78 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index f1ba87a2635c..1cf1d284f733 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs
index 4a5e527df630..bc256be1ea79 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1699,7 +1699,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs
index 7724cc47e7e3..a3fbe08251a0 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs
@@ -118,7 +118,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs
index e0bbb6a90515..4cd64f8cfbd0 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index c227978f4c94..4c549d0b0c13 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 95e96c442bb9..eed2b499ad8a 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 538857e10d49..9ad7288dee19 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs
index 92a7d9bf8462..7759e1e17d39 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 78ba8e07009a..dcd8ac1b9a2b 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index f8350930f14a..d6d75a35d578 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 964f5b3ed00e..68d941a3d0dd 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs
index 0e3972e37a16..914fb011b3b6 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs
index 56424996d5c0..5f1fd6c6fe82 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 1e54eafcfa2b..d14f40675ef0 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 64b45c2a1d34..bd9abfb5330b 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs
index 90d78d2e066f..352f06d49187 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -150,7 +150,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -160,7 +160,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index bb87cf541324..86acdbef9c28 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs
index 4205752aa4d2..f4eec4a5d5b3 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs
index 399994e28dc2..f70ae70ab310 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs
@@ -103,7 +103,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -113,7 +113,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 1892a822d865..538fede8f102 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/User.cs
index 04daff1ed7be..3ba80694ac78 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/User.cs
@@ -264,7 +264,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs
index 29bde9dd1ac8..6ba6b5f02465 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs
@@ -108,7 +108,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs
index f60c1b215254..8c95f7355802 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs
@@ -172,7 +172,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index f0e86093b153..b7afd8a130cd 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -149,7 +149,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs b/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
index e55c4400d994..b0999ebf8aa0 100644
--- a/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Model/Person.cs b/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Model/Person.cs
index a8f07fd13d7a..4373e60686d9 100644
--- a/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Model/Person.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Model/Person.cs
@@ -106,7 +106,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -116,7 +116,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
index f013ab58aff2..f985f250f712 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Apple.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
index d2e3592a7114..b1b959afea24 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Banana.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
index d283da3cd5f9..f5af2e0caaf1 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -109,7 +109,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
index 8cfcda99a1d7..0754094c6901 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Apple.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
index 2be6e1b0501c..893a8623dc4f 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Banana.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
index ebcf62ab1443..55d4d2ba7126 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Model/Fruit.cs
@@ -108,7 +108,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Activity.cs
index 0baba23ccf52..f51e85f459e9 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 38e288cbbe85..852840c03144 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 8b63e560e3c3..78fd02d9e8fd 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Animal.cs
index 2407c49d6e87..b2d1a75913d7 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
index af6d432b7f9f..dc2f82b08fea 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Apple.cs
index e9c5013017fa..6bb83229b568 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
index 00162b94b0a8..e2e05c94f8ed 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index c97d9f91e1ef..eb63c621a9a4 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 20a8f6f9d088..da1c5c5cebc0 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
index 4d27ed8f58a1..1352957ba7d9 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Banana.cs
index 83737b32ed0d..b1a974648b90 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
index 8a4e8157fdc9..129c725f3ad3 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
index ed964f1dea99..646a24850fab 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Category.cs
index adfb6bb5076a..9428697a62bc 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
index eafd95906774..3782731ad18f 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 2f4b08d39f90..46448cd6084a 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 4148a0a4efe9..60afe853895b 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
index 0d9208ff5c4e..e0e0c98a773c 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
index 379d700af3f1..d0290d43113e 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
index c5b98a8acf8b..6b4568ab3225 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -201,7 +201,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/File.cs
index 978be6bf3452..795846b7c8e3 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c3596b4f7d79..04a0d237ccf1 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Foo.cs
index ebfbcac41665..9c73bd652db4 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 07043466e6a3..fd03617ed923 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
index 36ec7c7b26eb..92d5f91c29c3 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
index 42999757b8fa..784b5dc9af79 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
index 3322eb6f7e15..c9077bcb304a 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index a1263c37991a..dd0923639f7f 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index b0087e834c23..f6248cd06db8 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/List.cs
index 55083fed4563..c88f88c56abf 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index c98cd6b621e8..87f641bef11c 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
index 97bb8da7ad8a..951533a3e5a4 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MapTest.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 1a9b032ad804..c78165a70a1c 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index a644a5c3610f..8f9499a29e1d 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
index def0526bc48f..22bc58e809f4 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 5309a1772be0..23e842d9ff6a 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
index 3bc3896d56ff..c8d4e7d606a7 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
index 4073dbdb33e1..75f0c7edf6cc 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
index 8fc27e9fd8a5..75c71d412d83 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Name.cs
index 7f925e162542..40b9dc332552 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
index e31d9a77da8b..4e8a345d148f 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index b95f5fdcd5f3..aadb184abe88 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
index 2c65bf4c6c90..d680ec1c8ca9 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index f660f8b075be..6517e80cc973 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Order.cs
index 5fe551909fc4..08a648bb6ce7 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Order.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3fcb5458c381..6c64e64ba940 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Pet.cs
index 58d614666577..5765b5dd4290 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Pet.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index e91a9b116ec8..d1c286b8a4ef 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
index f82558027777..c4d05a7678b9 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -618,7 +618,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Result.cs
index d2ca3e9ac752..207fdeb6b9a2 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Return.cs
index 7d3365117205..07cc2b095b7b 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 821bafb5c74b..a69fa50a852d 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index e399e3ef9755..068d6270fe9e 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ebbf47e9c5f1..88c1bbf92490 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Tag.cs
index ef8ec55b20d0..107b07e38baf 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index fbdb0cd4a585..9be93e830da8 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index db4b142b687a..214a5b29a17b 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
index 91b0e0dfec84..2322e3b3cfb6 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -91,7 +91,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 3852ce1829df..a760f8d9ca06 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
index a7c1f97f6c8b..4f754172a639 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/User.cs
index 4ffb503161f7..aaf4092782ab 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Whale.cs
index 087642453d9b..5b5788907f9a 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
index 1f3158514d78..3fc95eeebf2a 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/Zebra.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 262803184890..fc8c07b8e164 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs
index 68e6556fe628..b18c293835f7 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Activity.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 8e4f68052139..127001f2b83f 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 18942823ef58..bf0e4e9bdcc5 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -195,7 +195,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs
index ca288e27e247..f6b242de1261 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Animal.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -100,7 +100,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs
index 429966bbadbd..416750262075 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs
index beb6f775284d..95c0370d683f 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Apple.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs
index bd54b3a2f52e..dd0e6f3e1072 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 4c069dc4ce82..105058141730 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index e8675a5a80a1..c0d5a75cd5ba 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs
index 43d194bb8b48..0225bed3c4f3 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs
index 2d6ae93660d9..05c1b9d6bb9c 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Banana.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs
index 3d0a61033423..3279bfa089e7 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs
index 1ebe60f765ac..9e6b7504defb 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs
index 8fd8c1a51c41..8b18172f4fe1 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -163,7 +163,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs
index edd7f8dacb8b..b84366ca5875 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Category.cs
@@ -91,7 +91,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs
index 69e62afafe0c..9c8c7e8867f2 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index f1bad4d77735..e50bd7be664c 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs
index 8bb1b45865ba..32ca88b4ba2a 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 545fa73801f7..e0959bac1663 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index f731dd97b377..387754a117f1 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs
index 7f00e7b6b074..a612d22c6da2 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Drawing.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs
index 1bb43e6a8ee3..88885587ba62 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -84,7 +84,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs
index c8f09af033bd..d0518894c929 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -230,7 +230,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs
index 915278e2837c..24b0e71d7063 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -686,7 +686,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 87ed595f4a42..d021c1a06c0e 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs
index 41c218eaf072..b797c30e9856 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/File.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 11f2f7e2ebb7..0625b546c919 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs
index d6a71b2f68e6..b6918e158aa7 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Foo.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 23310da4d01b..095432b6acd5 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs
index d5e6ef21ec27..524db225d229 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -485,114 +485,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -638,13 +638,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs
index 1cb37dc50b07..a4308c32d8b6 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Fruit.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs
index 13e9d1a5b6bf..d561a09a3804 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs
index 87badf71a4a9..59c8e02abb38 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -102,7 +102,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 001d612fc862..3eed79308214 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -74,7 +74,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -84,7 +84,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 7dfecca3e4c2..c4efe268aeaa 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index 68c52ea737b4..b5a27da55cdd 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index c1cb9bc77c58..e3efc7dd5bb2 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -209,7 +209,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 5b6eed7047ce..e52e9a1a001f 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -77,7 +77,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs
index 64f7d9f90a6c..33f524131799 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/List.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index 4113e1c396ec..37c9f514e77a 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs
index 8dae459101ba..3a7ee353247d 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Mammal.cs
@@ -102,7 +102,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -112,7 +112,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs
index 03fef3b9ce60..7153674bfcee 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MapTest.cs
@@ -196,7 +196,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 18da3c77dd48..ed4dfe88eef1 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index f2ba03f1e0d4..78e4de989031 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -135,7 +135,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 9d674926e216..ed5145de010f 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 1a42741423ae..6811c075b9ca 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -132,7 +132,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index a509a5ff65ef..36b610c40036 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs
index f036240b579b..26efa752a2a8 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs
index e4ae282ec9b6..e57fb5119e68 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs
index d0bd57ad9e25..473d5ab1b8bd 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs
index 5ed720c3ccc4..c80eb6ebabbc 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Name.cs
@@ -164,7 +164,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 0c5df34a03d3..92db35933844 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs
index d8f280bd09c8..fbb77b864ef8 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -258,7 +258,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 09d2f81739a0..a68f5745d461 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs
index 765b17c09b94..267ac32bcb43 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs
index 9a7e8b24d204..8b315295c063 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index 978db5f11c6e..b381ed067450 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs
index be2cec490d8f..29000bb7adad 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs
index 1d24837d0117..3b714c322a27 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Order.cs
@@ -245,7 +245,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3eac7fb0efdf..7f9b2c097b91 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs
index 1607391d0075..4ea8d65be836 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Pet.cs
@@ -231,7 +231,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs
index e5c2b80f4295..99978f33879e 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Pig.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 1caaf6f6b92c..c5c884525043 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs
index 52b8cdfb1355..8d9a23c043bd 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 4596a6492745..591fe6abde97 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 8978d99739e1..259cafd3ed88 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs
index 5c1539bc201d..dfb0a1c64797 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1698,7 +1698,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs
index 33001f356a9b..0d7325a10e96 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Result.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs
index 86dbc4c2a190..e39fbf85010d 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Return.cs
@@ -116,7 +116,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 428fb58213c1..d4488fa657e9 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 8d965d718002..181c17a16cee 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index f8f7b31fde34..1ee8c0944c08 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs
index 76cdea3c0f13..23abcc3c4eb2 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Shape.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs
index b014ebce7804..b42cb4fea949 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index ab53a15de52d..95fd9f19ca5a 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -87,7 +87,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -97,7 +97,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 31e83cc8e021..58738425c74d 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs
index 781119dc84e7..b6bd9fb06e40 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs
index f12bda6458a9..d2e8171103be 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Tag.cs
@@ -98,7 +98,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 21e6e3486671..cd1413cf832e 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index d58357a22252..f36b33493e94 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs
index 927eb828c42c..6f093288a67d 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -149,7 +149,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -159,7 +159,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index b214297afab7..eca952b8d177 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs
index 64f9ac9c690b..5308a3f6befa 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TestResult.cs
@@ -116,7 +116,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs
index 039a2351c3f7..72190dd711ec 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Triangle.cs
@@ -102,7 +102,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -112,7 +112,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs
index e2fc8b97c357..4bc6ca701e71 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs
index b3fe51551553..8f0a63079211 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/User.cs
@@ -263,7 +263,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs
index 2fad1c319e4b..26cbad6318d8 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Whale.cs
@@ -107,7 +107,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs
index 31b6a8d4d271..6fe7ebd5a7b4 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/Zebra.cs
@@ -171,7 +171,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index e4137d8207e7..0e0944558e5d 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -148,7 +148,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Apple.cs
index f013ab58aff2..f985f250f712 100644
--- a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Apple.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Banana.cs
index d2e3592a7114..b1b959afea24 100644
--- a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Banana.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
index 3bb11c348e51..ba9946bc000b 100644
--- a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -122,7 +122,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Orange.cs b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Orange.cs
index 8895e46f2556..cde52f9eeab0 100644
--- a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Orange.cs
+++ b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Model/Orange.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index 0baba23ccf52..f51e85f459e9 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 38e288cbbe85..852840c03144 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 8b63e560e3c3..78fd02d9e8fd 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index 2407c49d6e87..b2d1a75913d7 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index af6d432b7f9f..dc2f82b08fea 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index e9c5013017fa..6bb83229b568 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 00162b94b0a8..e2e05c94f8ed 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index c97d9f91e1ef..eb63c621a9a4 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 20a8f6f9d088..da1c5c5cebc0 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 4d27ed8f58a1..1352957ba7d9 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index 83737b32ed0d..b1a974648b90 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index 8a4e8157fdc9..129c725f3ad3 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index ed964f1dea99..646a24850fab 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Category.cs
index adfb6bb5076a..9428697a62bc 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index eafd95906774..3782731ad18f 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 2f4b08d39f90..46448cd6084a 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 4148a0a4efe9..60afe853895b 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index 0d9208ff5c4e..e0e0c98a773c 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index cd2dcaa56797..9fa60dc4ea9d 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -228,7 +228,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index 92ecefeb9edd..4885e2fd5b9e 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -684,7 +684,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/File.cs
index 978be6bf3452..795846b7c8e3 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c3596b4f7d79..04a0d237ccf1 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index ebfbcac41665..9c73bd652db4 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 07043466e6a3..fd03617ed923 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 36ec7c7b26eb..92d5f91c29c3 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
index 42999757b8fa..784b5dc9af79 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
index 3322eb6f7e15..c9077bcb304a 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index a1263c37991a..dd0923639f7f 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index b0087e834c23..f6248cd06db8 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/List.cs
index 55083fed4563..c88f88c56abf 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index c98cd6b621e8..87f641bef11c 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index b5299c925ca4..368d85aace86 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -194,7 +194,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 1a9b032ad804..c78165a70a1c 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index a644a5c3610f..8f9499a29e1d 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index def0526bc48f..22bc58e809f4 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 5309a1772be0..23e842d9ff6a 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 3bc3896d56ff..c8d4e7d606a7 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index 4073dbdb33e1..75f0c7edf6cc 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 8fc27e9fd8a5..75c71d412d83 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 7f925e162542..40b9dc332552 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index e31d9a77da8b..4e8a345d148f 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index b95f5fdcd5f3..aadb184abe88 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index 2c65bf4c6c90..d680ec1c8ca9 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index f660f8b075be..6517e80cc973 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 1fa14c72cc2f..7a44d1816288 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -243,7 +243,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3fcb5458c381..6c64e64ba940 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index f3b9599a1325..afcb52da70b3 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -229,7 +229,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index e91a9b116ec8..d1c286b8a4ef 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index b6e1fd992a57..559718eef568 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1696,7 +1696,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Result.cs
index d2ca3e9ac752..207fdeb6b9a2 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Return.cs
index 7d3365117205..07cc2b095b7b 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 821bafb5c74b..a69fa50a852d 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index e399e3ef9755..068d6270fe9e 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ebbf47e9c5f1..88c1bbf92490 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index ef8ec55b20d0..107b07e38baf 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index fbdb0cd4a585..9be93e830da8 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index db4b142b687a..214a5b29a17b 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
index 3812a5f24758..2b4582eed5a3 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -157,7 +157,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 3852ce1829df..a760f8d9ca06 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
index a7c1f97f6c8b..4f754172a639 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/User.cs
index 4ffb503161f7..aaf4092782ab 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index 087642453d9b..5b5788907f9a 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index c2944781b24a..b345c0cd90dc 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -169,7 +169,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 959d2b03efe1..baaf025cdf9c 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -146,7 +146,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs
index 46121c8de25f..cf7f68a295a7 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Activity.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 5beaf95a3b55..5b3cc712de8b 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index b5322aa98c71..22a14542e350 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -196,7 +196,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs
index a71f0e5513d5..8131847e5896 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Animal.cs
@@ -91,7 +91,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -101,7 +101,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs
index ccd192b48a91..ffef8e4c1e88 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs
index 43c476af80c8..765c0ce4833c 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Apple.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs
index 0a0d2c56ffe1..931572f0dd29 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 0a84f33c9a4c..cd749ab1e3ac 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 26752a0cd36a..b0cc38229098 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs
index 944aa9287a73..b5dc90bd8462 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs
index 572e40e82582..34fd1bd73ac1 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Banana.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs
index bd71081f4354..f483a58269d9 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs
index b291a9e0675e..bb5a4a24d1d8 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs
index 0aff545dd56c..8ee757ad4d93 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -164,7 +164,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs
index a0cddb6d5d49..e15bd27efc2c 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Category.cs
@@ -92,7 +92,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs
index 1c0e9bb09aaf..297907a07938 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index a45a9e372eaf..15c826f538ca 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs
index 56be838031d7..3ab0184bfee5 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index a7a6859eb792..088bd36f7813 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 037467af4fd6..de5675e6e69f 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs
index 77792593add9..679e9cae14e7 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Drawing.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs
index bf2eabddedc5..735180ecd837 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -85,7 +85,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs
index 58a45a6a87cb..6b921e7c3a13 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -231,7 +231,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs
index 8f217f08d673..fb6bed674407 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -687,7 +687,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index c713c15e8e75..fe254376caf2 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/File.cs
index d63a071c30ae..d8d27797c621 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/File.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 667548469483..8531aa1826de 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs
index 189b130ccc4d..eea687ce11b9 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Foo.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index c8c5fa2a5b55..1135e0e3f1e2 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs
index 904cfb7c2d27..dd27824ed852 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -486,114 +486,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -639,13 +639,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs
index 5e9fa4564a89..faa29c9f5d95 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Fruit.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs
index 40a9aaf3e761..055e99668c60 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs
index 3781db9127c1..04c8c81b09cb 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -103,7 +103,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index ae9897dd949a..6d5ab52e2a83 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -85,7 +85,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 267a9bd7253d..8b4ec708d844 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index eb10f70fc159..fd5a1217a5c5 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index a5a551d58f03..1f83a7746e58 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -210,7 +210,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 18af0f861459..3bb832b139ee 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/List.cs
index 664fa067d24c..9dfd448b7e09 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/List.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index fbd2d2eb5273..2cf4c582f440 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs
index 6fd97f187117..1f96c8cf478e 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Mammal.cs
@@ -103,7 +103,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -113,7 +113,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs
index 15717778c839..654138d859fe 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MapTest.cs
@@ -197,7 +197,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index e6d8bd647e7a..7c59091d976b 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index b88a7e3c06af..f133840f6eb2 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -136,7 +136,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 0cf6230eb6bf..90b0d2773ad3 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 056b2b994649..8ef84d0e9496 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index e345c816ef94..91d296ad1073 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs
index 2548f40af76e..61592492cbbb 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs
index bac80386c438..d4bc1846a6d5 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs
index 3058a0066248..ab3f01486445 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs
index 3ce1f23d1746..dd4a4198792f 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Name.cs
@@ -165,7 +165,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 3db174a72bf7..429d00bbd1d6 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs
index 151ae9462421..0624c8bcd173 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -259,7 +259,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 7aa2022a3dbe..ad76f0195476 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -84,7 +84,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs
index b094f730ebc4..41885b4ce7d6 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs
index d8a6197c7490..441aa6537a89 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index a6c1d895cfda..2ba29dccf002 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -134,7 +134,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs
index 8bca9c113496..a82cef00ef30 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs
index 969537d113a7..ef0f880c2f26 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Order.cs
@@ -246,7 +246,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs
index 5e1a645aa922..aa2e44423b3e 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs
index 71c2b601e315..adb4cc86726e 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Pet.cs
@@ -232,7 +232,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs
index b3abfe311cca..40bdd7cdc98b 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Pig.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index e0baef9347bc..bb23a0e706e9 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -118,7 +118,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs
index 850de679ebf5..409b7ef3afc3 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 03646d05416b..c8b23b20ef78 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index f1ba87a2635c..1cf1d284f733 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs
index 4a5e527df630..bc256be1ea79 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1699,7 +1699,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs
index 7724cc47e7e3..a3fbe08251a0 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Result.cs
@@ -118,7 +118,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs
index e0bbb6a90515..4cd64f8cfbd0 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Return.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index c227978f4c94..4c549d0b0c13 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 95e96c442bb9..eed2b499ad8a 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 538857e10d49..9ad7288dee19 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs
index 92a7d9bf8462..7759e1e17d39 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Shape.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 78ba8e07009a..dcd8ac1b9a2b 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index f8350930f14a..d6d75a35d578 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 964f5b3ed00e..68d941a3d0dd 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs
index 0e3972e37a16..914fb011b3b6 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs
index 56424996d5c0..5f1fd6c6fe82 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Tag.cs
@@ -99,7 +99,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 1e54eafcfa2b..d14f40675ef0 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 64b45c2a1d34..bd9abfb5330b 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs
index 90d78d2e066f..352f06d49187 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -150,7 +150,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -160,7 +160,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index bb87cf541324..86acdbef9c28 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -83,7 +83,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs
index 4205752aa4d2..f4eec4a5d5b3 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TestResult.cs
@@ -117,7 +117,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs
index 399994e28dc2..f70ae70ab310 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Triangle.cs
@@ -103,7 +103,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -113,7 +113,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 1892a822d865..538fede8f102 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -76,7 +76,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/User.cs
index 04daff1ed7be..3ba80694ac78 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/User.cs
@@ -264,7 +264,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs
index 29bde9dd1ac8..6ba6b5f02465 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Whale.cs
@@ -108,7 +108,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs
index f60c1b215254..8c95f7355802 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/Zebra.cs
@@ -172,7 +172,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index f0e86093b153..b7afd8a130cd 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -149,7 +149,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs b/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
index e55c4400d994..b0999ebf8aa0 100644
--- a/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
+++ b/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
@@ -90,7 +90,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index 404476d906b0..b16edf9585ec 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 46ae0e3f391d..791135466d90 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index e01cfeffeb0d..32d404f7517b 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -193,7 +193,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index 1f0daf2c9e58..b47f118fa92d 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -88,7 +88,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -98,7 +98,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index 5fd2aa296926..bfceb53e9c48 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index ef8268a90a59..91ac5a77261a 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.ColorCodeOption.Value != null) {
                 // ColorCode (string) pattern
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 4938fc5a2e5b..d025c754f594 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index d085ea5e2d2c..970a9992550b 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index dc3b303411ef..95a13de67b5a 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index eaf99dd9f801..04441ef4f8dc 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index 32eea508145d..2259033dfd28 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index 42d1bc50f756..1049c3908fb3 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index d39d4142e341..459e3de6ddab 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index 94ce156e0bf6..ae87e9aa15bd 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -161,7 +161,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs
index 062bc4656542..278a9393a1c8 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -89,7 +89,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 15973b9e79fa..4bfeb403a9af 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 4d63d4298338..6e88bf9a02c6 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index e1e4d5cd40b2..24de461fc58d 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 84207ba12890..2b49d4004c96 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 747fbc7166f1..d3e470b96e7f 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index 28b81cba6536..1e0d226457ce 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
index c92e899b7d38..dda227d34f94 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index a1790a1a6ea3..07139226b993 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -228,7 +228,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index a5e46b184b61..55fbc1964ebf 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -684,7 +684,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8a2609aae4e2..da412f6cdda5 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs
index 028476ef05b2..1db7613177ff 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index e7f69a24ef3d..01b95e690f2a 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 8620b135a5d6..fbac0b2823ca 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index d0aa9bc4699a..078883656dba 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 27c50ce1bbe3..165f723307f4 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -483,114 +483,114 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             // Double (double) maximum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.DoubleOption.IsSet && this.DoubleOption.Value < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             // Float (float) maximum
             if (this.FloatOption.IsSet && this.FloatOption.Value > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.FloatOption.IsSet && this.FloatOption.Value < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Int32 (int) maximum
             if (this.Int32Option.IsSet && this.Int32Option.Value > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32Option.IsSet && this.Int32Option.Value < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32RangeOption.IsSet && this.Int32RangeOption.Value < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64NegativeOption.IsSet && this.Int64NegativeOption.Value > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusiveOption.IsSet && this.Int64NegativeExclusiveOption.Value <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64PositiveOption.IsSet && this.Int64PositiveOption.Value < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusiveOption.IsSet && this.Int64PositiveExclusiveOption.Value < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Integer (int) maximum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.IntegerOption.IsSet && this.IntegerOption.Value < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             if (this.PatternWithBackslashOption.Value != null) {
@@ -636,13 +636,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // UnsignedInteger (uint) maximum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedIntegerOption.IsSet && this.UnsignedIntegerOption.Value < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             yield break;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
index 8ad0d64c1be5..ba7eb93c2ec2 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Fruit.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
index 7dc511018ade..88686dd4a32e 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/FruitReq.cs
@@ -78,7 +78,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
index 4b122a792d91..02322bad0ce5 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/GmFruit.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 17fc21130302..68549a5c5c11 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -72,7 +72,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -82,7 +82,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 0f8656c85e8e..9d0425a76335 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index ffd2310b3213..0182e92ea13d 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index 154e205c9166..96fa99ca40b1 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 60c9114c5791..a51918200d22 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -75,7 +75,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs
index 2f275baa700f..c11932926f79 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index ab45fc36b6c7..22e94ce9d28e 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Mammal.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
index be313538ae71..d5098720531e 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Mammal.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index 888d9392b1f6..d532f0f9c93a 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -194,7 +194,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index bb4959ca5175..54aac5d896e1 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
index b8fc88212401..c34b0aeb80fd 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOfContent.cs
@@ -133,7 +133,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 706d7fc6b64c..d2e512b7c931 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
index 2367d300da72..65ed21f4c667 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOfContent.cs
@@ -130,7 +130,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 3c3c09b4f2f5..4e655fdffe1f 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -128,7 +128,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // UuidWithPattern (Guid) pattern
             Regex regexUuidWithPattern = new Regex(@"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", RegexOptions.CultureInvariant);
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 121a21a30b23..0e8b992439e4 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index aceb8d425b94..bf7af7d752d9 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 2d1e29add011..ed31adedc185 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 4517587d378c..faee8445cbd4 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index c67599315467..24f99a5c6edd 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index f32957f8dc40..4b1de3bbf890 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -256,7 +256,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 450d192600cb..876ec6812878 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -81,7 +81,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
index 78d92ffdff79..8ecc512f4f49 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableShape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index 1ef25662ecf5..81c3755c3a0f 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index e71b7f7939c3..1416a7d02013 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -131,7 +131,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
index 6a272e1b6e8a..f7348b0bcbca 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/OneOfString.cs
@@ -70,7 +70,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 42136304b77a..a9aad4e98bc4 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -243,7 +243,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index c455c6d87241..0d78e7d0dcd5 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -112,7 +112,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index b11ba88083fc..f4ce1f31fb1a 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -229,7 +229,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pig.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pig.cs
index d7cf2044a024..97b772df60ec 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pig.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pig.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
index 75d26e5651e5..affea08f6f8a 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/PolymorphicProperty.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
index eaf989412ccc..e7354b6cd991 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Quadrilateral.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 860e115ad157..b61e1e1f6db0 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 40b6be4e4165..d759665cf4ab 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index 3aa2cc985648..e6715816b6ca 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1696,7 +1696,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Result.cs
index b4d4a5929709..fb9df5a6ecef 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Result.cs
@@ -115,7 +115,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs
index 7a33ca9ddb15..1422ed929401 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 8a95a1148df5..3c499e2d5c1e 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 2b94fa2026fd..c58167c8073e 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 498f37a358c7..c321e59826b9 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Shape.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Shape.cs
index 71a1d4cb0ec0..83810bda65c9 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Shape.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Shape.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 356459fbd154..af4541cd3f85 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
index 17df1392c391..28af35c608f9 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeOrNull.cs
@@ -85,7 +85,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -95,7 +95,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 98336ddd3bbf..3fa8e3a58ceb 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -82,7 +82,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index ad59ab442459..9a1d720f4388 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index e2213d2d75e1..50857c190256 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -96,7 +96,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bae68ea3d331..3a4b6246362c 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 272a27134f49..c77826536550 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
index 3812a5f24758..2b4582eed5a3 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -147,7 +147,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -157,7 +157,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 9c44f845a1ac..c44e3d4fcc62 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -80,7 +80,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
index d8f5f794a076..9f3a467c19f5 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
@@ -114,7 +114,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Triangle.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
index 8a2e561cc3c2..a922be0a9749 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Triangle.cs
@@ -100,7 +100,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -110,7 +110,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 9a4682473fb4..6511c9cc0bf5 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -73,7 +73,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs
index f0bc20b7756d..652b50ab6da7 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -261,7 +261,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index e43fef0983cd..109770eb7140 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -105,7 +105,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index d501d9990668..43e1a5acdffb 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -169,7 +169,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 55b029c7fd90..a5e10fb39370 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -146,7 +146,7 @@ public override string ToString()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Category.cs
index cd404ece441c..3a25bcd80c70 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Category.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Name != null) {
                 // Name (string) pattern
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Pet.cs
index eb55ecb5b61a..bb2ce691ce9e 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Pet.cs
@@ -232,7 +232,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Tag.cs
index 64e704f6f846..ea74aa70c108 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Tag.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index b08438555ccb..f94e688a286f 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index a7dc90608220..68d0ea70b988 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 35cb11b25903..bb83a959f820 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -216,7 +216,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index d9839dfdb7a2..e46e867b6caa 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -165,7 +165,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index ac0d3f572d43..1ab75c4386df 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -147,7 +147,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index 673530886c3a..8cea7108ba4c 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index a21b749c0620..ecfa213464e0 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -132,7 +132,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index f89102289e66..cc374ad325da 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index ff7ee14ed1da..942fe9acfe36 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 50c5dea2aca9..bc766a16df36 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index caa5bbd6354a..cac9c31198c9 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index 9babb83e99f6..ab059944fa69 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index 3c9d8fddeb68..db7a6ce0d9ff 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index 2d0c692c8e3d..6ce144bfaef2 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -190,7 +190,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Cat.cs
index 3ec666234963..145e37de1514 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Cat.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -143,7 +143,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs
index b4f5b1831b1c..bb7328d6adab 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -147,7 +147,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
index 9f1a34942616..c1cc938b480b 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -157,7 +157,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -167,7 +167,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 0751ba67ee91..1a21693357de 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index e6bc8973e218..0f352ada1361 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
index bb10b291e828..6a81f8039925 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -172,7 +172,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index 047100d98c2c..659bdfb86c60 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index ff4cf78e05d7..14026c6e3b29 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -127,7 +127,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 07a0e8e0425f..33040b3aedd2 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
index 6283f40b7a43..69776f41cc04 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
index 087d74c36758..02ad1c4e421a 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Dog.cs
index 33ffeca6830c..72a9029d58d7 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Dog.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -146,7 +146,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index 575712f265f0..8ea510e5b03b 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
index 52bb01e48a3c..f69de9019080 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -150,7 +150,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index 8c561798337a..c957fda96ba9 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -172,7 +172,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index c8bb688e948b..181e4681429e 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -370,7 +370,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index dd4afe27da59..eec0acd6dfee 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/File.cs
index befc2c2fe19d..6f68f053e8b7 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -125,7 +125,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 8d08e0744456..2bf98d9b27cf 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 10c97e7ed29c..0622c6e23b57 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -125,7 +125,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index c4eef623e65a..81119a9984d3 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 31cc93ec432b..68809176ea21 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -457,114 +457,114 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32Range > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32Range < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64Positive < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64Negative > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusive < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusive <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -579,13 +579,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index f3d60eb6a79c..646fb027de67 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 8ac3489e8b7a..79815e1812e2 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index c1791fadad71..1da5aa3f6cc4 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index 7a4fc9123051..e4e7a1ff9902 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -213,7 +213,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 0e2b942360c2..b3930838fbda 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/List.cs
index f5c20b9afef9..80fa8567a799 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index db0dc595908e..eaa4c72410fe 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index dc23b390e062..8f7a628082d1 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -182,7 +182,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 0fa84d63801f..8b4b25d45640 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index ddc1c8b66ab0..e4f8ac9e463e 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index f888850d677c..a405e8b96c9e 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index ace2f3c355bf..8a9347a607a2 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index e3aad5bb540a..b0af8f4e5419 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 777a9308be8c..936bdba9ab38 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 03994dbe545b..3eee98cf4ea6 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -174,7 +174,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 5246937f6e66..ccf96d8338d6 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -147,7 +147,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index a664857f3d35..0d3ae00b30cc 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -267,7 +267,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index b3e90dc62116..66223cee5cd9 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -127,7 +127,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index 7370cf5f4f62..447250a5e49d 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index ac765f067af7..581d4a78813f 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 25b3fe0b2781..1660d8a1569e 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -204,7 +204,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index 5d5dfb6d34f0..6ca0ace2f363 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -144,7 +144,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
index 98e7574e092e..9f866c87f8b7 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -134,7 +134,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index dcb433325749..e27274ccaf6c 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -231,7 +231,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index f0f16774eff6..83df5e4e330c 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 90d841f4d766..04d2662cec8b 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -143,7 +143,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index f14b947cd740..083a0de88f85 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1038,7 +1038,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Result.cs
index 8e00fc89a6f2..f61ba41ab9e4 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Result.cs
@@ -153,7 +153,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs
index 533ce598cc88..6e961b5c1bb1 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -178,7 +178,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 557aec62e70e..e0b336bc88f6 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index ef6b7febbfc9..41b4add2a76e 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 5d867c7256f4..42fb0e175fbd 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index ca231858e2f8..12bb86c29ec3 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 5c5f3b24b050..75cd4c8c12cf 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index d89637d463ac..baf97437afe0 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index 75be41dff9cf..4a5dc9a0cd68 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 043658b8180e..30e58faf89ac 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 3b8b80bbb115..1b0ca556f754 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
index 7771e8a2a5f2..fb834c69a47f 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -170,7 +170,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -180,7 +180,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index c746b7d07023..e7f385f2e3a7 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
index 7023e1e52574..db783afe5b67 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 0f5a61d0df54..4ba1ff675646 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/User.cs
index 910903ecfb5a..bcef6b2756db 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -266,7 +266,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index e49f7867fdd8..26ae9c0b3e73 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -157,7 +157,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index 34775905ac98..eec9c958e36f 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -172,7 +172,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 8e919c1af849..675c0dd8a8b3 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Category.cs
index cd404ece441c..3a25bcd80c70 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Category.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Name != null) {
                 // Name (string) pattern
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Pet.cs
index eb55ecb5b61a..bb2ce691ce9e 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Pet.cs
@@ -232,7 +232,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Tag.cs
index 64e704f6f846..ea74aa70c108 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Model/Tag.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index b08438555ccb..f94e688a286f 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index a7dc90608220..68d0ea70b988 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 35cb11b25903..bb83a959f820 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -216,7 +216,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index d9839dfdb7a2..e46e867b6caa 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -165,7 +165,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index ac0d3f572d43..1ab75c4386df 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -147,7 +147,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index 673530886c3a..8cea7108ba4c 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index a21b749c0620..ecfa213464e0 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -132,7 +132,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index f89102289e66..cc374ad325da 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index ff7ee14ed1da..942fe9acfe36 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 50c5dea2aca9..bc766a16df36 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index caa5bbd6354a..cac9c31198c9 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index 9babb83e99f6..ab059944fa69 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index 3c9d8fddeb68..db7a6ce0d9ff 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index 2d0c692c8e3d..6ce144bfaef2 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -190,7 +190,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Cat.cs
index 3ec666234963..145e37de1514 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Cat.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -143,7 +143,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Category.cs
index b4f5b1831b1c..bb7328d6adab 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -147,7 +147,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
index 9f1a34942616..c1cc938b480b 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -157,7 +157,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -167,7 +167,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 0751ba67ee91..1a21693357de 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index e6bc8973e218..0f352ada1361 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
index bb10b291e828..6a81f8039925 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -172,7 +172,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index 047100d98c2c..659bdfb86c60 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index ff4cf78e05d7..14026c6e3b29 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -127,7 +127,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 07a0e8e0425f..33040b3aedd2 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
index 6283f40b7a43..69776f41cc04 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
index 087d74c36758..02ad1c4e421a 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Dog.cs
index 33ffeca6830c..72a9029d58d7 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Dog.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -146,7 +146,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index 575712f265f0..8ea510e5b03b 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
index 52bb01e48a3c..f69de9019080 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -150,7 +150,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index 8c561798337a..c957fda96ba9 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -172,7 +172,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index c8bb688e948b..181e4681429e 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -370,7 +370,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index dd4afe27da59..eec0acd6dfee 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/File.cs
index befc2c2fe19d..6f68f053e8b7 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -125,7 +125,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 8d08e0744456..2bf98d9b27cf 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 10c97e7ed29c..0622c6e23b57 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -125,7 +125,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index c4eef623e65a..81119a9984d3 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 31cc93ec432b..68809176ea21 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -457,114 +457,114 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32Range > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32Range < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64Positive < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64Negative > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusive < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusive <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -579,13 +579,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index f3d60eb6a79c..646fb027de67 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 8ac3489e8b7a..79815e1812e2 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index c1791fadad71..1da5aa3f6cc4 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index 7a4fc9123051..e4e7a1ff9902 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -213,7 +213,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 0e2b942360c2..b3930838fbda 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/List.cs
index f5c20b9afef9..80fa8567a799 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index db0dc595908e..eaa4c72410fe 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index dc23b390e062..8f7a628082d1 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -182,7 +182,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 0fa84d63801f..8b4b25d45640 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index ddc1c8b66ab0..e4f8ac9e463e 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index f888850d677c..a405e8b96c9e 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index ace2f3c355bf..8a9347a607a2 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index e3aad5bb540a..b0af8f4e5419 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 777a9308be8c..936bdba9ab38 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 03994dbe545b..3eee98cf4ea6 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -174,7 +174,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 5246937f6e66..ccf96d8338d6 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -147,7 +147,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index a664857f3d35..0d3ae00b30cc 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -267,7 +267,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index b3e90dc62116..66223cee5cd9 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -127,7 +127,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index 7370cf5f4f62..447250a5e49d 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index ac765f067af7..581d4a78813f 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 25b3fe0b2781..1660d8a1569e 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -204,7 +204,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index 5d5dfb6d34f0..6ca0ace2f363 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -144,7 +144,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
index 98e7574e092e..9f866c87f8b7 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -134,7 +134,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index dcb433325749..e27274ccaf6c 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -231,7 +231,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index f0f16774eff6..83df5e4e330c 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 90d841f4d766..04d2662cec8b 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -143,7 +143,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index f14b947cd740..083a0de88f85 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1038,7 +1038,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Result.cs
index 8e00fc89a6f2..f61ba41ab9e4 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Result.cs
@@ -153,7 +153,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Return.cs
index 533ce598cc88..6e961b5c1bb1 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -178,7 +178,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 557aec62e70e..e0b336bc88f6 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index ef6b7febbfc9..41b4add2a76e 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 5d867c7256f4..42fb0e175fbd 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index ca231858e2f8..12bb86c29ec3 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 5c5f3b24b050..75cd4c8c12cf 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index d89637d463ac..baf97437afe0 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index 75be41dff9cf..4a5dc9a0cd68 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 043658b8180e..30e58faf89ac 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 3b8b80bbb115..1b0ca556f754 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
index 7771e8a2a5f2..fb834c69a47f 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -170,7 +170,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -180,7 +180,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index c746b7d07023..e7f385f2e3a7 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
index 7023e1e52574..db783afe5b67 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 0f5a61d0df54..4ba1ff675646 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/User.cs
index 910903ecfb5a..bcef6b2756db 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -266,7 +266,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index e49f7867fdd8..26ae9c0b3e73 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -157,7 +157,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index 34775905ac98..eec9c958e36f 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -172,7 +172,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 8e919c1af849..675c0dd8a8b3 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index b08438555ccb..f94e688a286f 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index a7dc90608220..68d0ea70b988 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 35cb11b25903..bb83a959f820 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -216,7 +216,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index d9839dfdb7a2..e46e867b6caa 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -165,7 +165,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index ac0d3f572d43..1ab75c4386df 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -147,7 +147,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index 673530886c3a..8cea7108ba4c 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index a21b749c0620..ecfa213464e0 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -132,7 +132,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index f89102289e66..cc374ad325da 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index ff7ee14ed1da..942fe9acfe36 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 50c5dea2aca9..bc766a16df36 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index caa5bbd6354a..cac9c31198c9 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index 9babb83e99f6..ab059944fa69 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index 3c9d8fddeb68..db7a6ce0d9ff 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index 2d0c692c8e3d..6ce144bfaef2 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -190,7 +190,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Cat.cs
index 3ec666234963..145e37de1514 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Cat.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -143,7 +143,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs
index b4f5b1831b1c..bb7328d6adab 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -147,7 +147,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
index 9f1a34942616..c1cc938b480b 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -157,7 +157,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -167,7 +167,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 0751ba67ee91..1a21693357de 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index e6bc8973e218..0f352ada1361 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
index bb10b291e828..6a81f8039925 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -172,7 +172,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index 047100d98c2c..659bdfb86c60 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index a824e70898f4..88ff6947ef90 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -128,7 +128,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 07a0e8e0425f..33040b3aedd2 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
index 6283f40b7a43..69776f41cc04 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
index 087d74c36758..02ad1c4e421a 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Dog.cs
index 33ffeca6830c..72a9029d58d7 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Dog.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -146,7 +146,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index 575712f265f0..8ea510e5b03b 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
index 52bb01e48a3c..f69de9019080 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -150,7 +150,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index 8c561798337a..c957fda96ba9 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -172,7 +172,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index c8bb688e948b..181e4681429e 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -370,7 +370,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index dd4afe27da59..eec0acd6dfee 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs
index befc2c2fe19d..6f68f053e8b7 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -125,7 +125,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 8d08e0744456..2bf98d9b27cf 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 10c97e7ed29c..0622c6e23b57 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -125,7 +125,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index c4eef623e65a..81119a9984d3 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 01d0c792593b..57e5b606ef16 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -458,114 +458,114 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32Range > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32Range < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64Positive < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64Negative > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusive < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusive <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -580,13 +580,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index f3d60eb6a79c..646fb027de67 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 8ac3489e8b7a..79815e1812e2 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index c1791fadad71..1da5aa3f6cc4 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index 7a4fc9123051..e4e7a1ff9902 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -213,7 +213,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 0e2b942360c2..b3930838fbda 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs
index f5c20b9afef9..80fa8567a799 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index db0dc595908e..eaa4c72410fe 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index dc23b390e062..8f7a628082d1 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -182,7 +182,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 0fa84d63801f..8b4b25d45640 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index ddc1c8b66ab0..e4f8ac9e463e 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index f888850d677c..a405e8b96c9e 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index ace2f3c355bf..8a9347a607a2 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index e3aad5bb540a..b0af8f4e5419 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 777a9308be8c..936bdba9ab38 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 03994dbe545b..3eee98cf4ea6 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -174,7 +174,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 5246937f6e66..ccf96d8338d6 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -147,7 +147,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index 13a5a2d0f617..102b987a860e 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -268,7 +268,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index b3e90dc62116..66223cee5cd9 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -127,7 +127,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index 7370cf5f4f62..447250a5e49d 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index ac765f067af7..581d4a78813f 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 25b3fe0b2781..1660d8a1569e 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -204,7 +204,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index 5d5dfb6d34f0..6ca0ace2f363 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -144,7 +144,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
index 98e7574e092e..9f866c87f8b7 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -134,7 +134,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index dcb433325749..e27274ccaf6c 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -231,7 +231,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index f0f16774eff6..83df5e4e330c 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 90d841f4d766..04d2662cec8b 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -143,7 +143,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index c91513201c08..fc9721c0fe88 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1042,7 +1042,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Result.cs
index 8e00fc89a6f2..f61ba41ab9e4 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Result.cs
@@ -153,7 +153,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs
index 533ce598cc88..6e961b5c1bb1 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -178,7 +178,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 557aec62e70e..e0b336bc88f6 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index ef6b7febbfc9..41b4add2a76e 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 5d867c7256f4..42fb0e175fbd 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index ca231858e2f8..12bb86c29ec3 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 5c5f3b24b050..75cd4c8c12cf 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -155,7 +155,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index d89637d463ac..baf97437afe0 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index 75be41dff9cf..4a5dc9a0cd68 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 043658b8180e..30e58faf89ac 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 3b8b80bbb115..1b0ca556f754 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
index 7771e8a2a5f2..fb834c69a47f 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -170,7 +170,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -180,7 +180,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index c746b7d07023..e7f385f2e3a7 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
index 7023e1e52574..db783afe5b67 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 0f5a61d0df54..4ba1ff675646 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs
index 910903ecfb5a..bcef6b2756db 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -266,7 +266,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index e49f7867fdd8..26ae9c0b3e73 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -157,7 +157,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index 34775905ac98..eec9c958e36f 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -172,7 +172,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 8e919c1af849..675c0dd8a8b3 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs
index c4d1476cb207..e9b9bbee9761 100644
--- a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -30,7 +30,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -71,10 +70,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -494,7 +493,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs
index 9edc5c28265f..a82f8d9e5342 100644
--- a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Category.cs
index 8099b7c64527..1d8cb064d8b7 100644
--- a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Category.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Name != null) {
                 // Name (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Order.cs
index 1b970204130f..71dab7d2aab3 100644
--- a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Order.cs
@@ -200,7 +200,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs
index 04d7c548cd3c..190eab494fbd 100644
--- a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs
@@ -231,7 +231,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs
index 1218e11890e6..39458d155e05 100644
--- a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/User.cs
index c36b491eeb54..93af5730614d 100644
--- a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Model/User.cs
@@ -209,7 +209,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
index a8f6dea4407b..e39e44dc8d81 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -30,7 +30,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -71,10 +70,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -494,7 +493,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index db5b8c45b8f2..e55a21587236 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index ea9a0dc0f39c..533a81d9b0b3 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 99aff9d787c3..a2a1793c3b67 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -215,7 +215,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index f6d7f1cf5b60..244914ede066 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -164,7 +164,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index 7dec589c62d6..49b4a2e3a078 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index 12fef1561aa0..59d1eb66813c 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 15d96e2ee292..4c6717e8671a 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -131,7 +131,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 6757590569e8..367cffebf5f3 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 054b6cdd404f..ab500c64e0a7 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 7c148fc567b2..a99e707db885 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index c506c26dbb8a..308f9fd10e6a 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index a95d29e6aa0b..5062a8c34de7 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index bdb255710665..ac0672979a77 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index bf185fe10e60..239c14fc1a92 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -189,7 +189,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Cat.cs
index b7a2c073c0cf..075f957164be 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Cat.cs
@@ -132,7 +132,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -142,7 +142,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs
index b56dfc0c4828..823821fc3e83 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
index 75760311e7b2..ce2550c74a1e 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -166,7 +166,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 66b8dbfc501f..6c7f38512827 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index b5cd8370cb9f..fa4d1f9e98f4 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index f3f19fce57f9..0ea24d160cef 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index e4660e563c78..41c78a93906b 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -126,7 +126,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 43886a5c8357..f1a47425f34e 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Dog.cs
index 57a7e340dd4e..be9a5889ef9e 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Dog.cs
@@ -135,7 +135,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -145,7 +145,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index f9918311cf5f..38561e69e644 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index 7a9834a78d18..9102c56cec8d 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index 0851264693b3..cbaef29ae70a 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -369,7 +369,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 373122a59235..6cf007da939f 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/File.cs
index 40dd973d3067..a4ef22ee1141 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c870be88db2f..3f45c47a6115 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 3108c8a86913..570e3de7f650 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 709031fd9398..e7ccfc43de0b 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index f036de12837b..cf8eeecd6f18 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -360,78 +360,78 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -446,13 +446,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 9d576878b233..9c5b047e85f0 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -150,7 +150,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 3c6298d7d8d2..2d4a1cd404f3 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index abb6777f0a75..67f7030ce8af 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 297e82fd9ba5..bdae3f577962 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/List.cs
index 7e4c1485e149..ec0286232f36 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index 57cc8110fbb8..3efdf1238452 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -138,7 +138,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index 64ca5484864e..f3bf0b27e67f 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -181,7 +181,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index c7684d040338..6e194e670356 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 38430dec6e6b..704488a0e32b 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index ec679f5c5bba..4467ab56f5d0 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 042125a808a5..d65f720a7540 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index 74b83092923f..5b0b4879e686 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 67847aa368e6..59474c83bf10 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 4eace322815d..288a511d8a01 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -173,7 +173,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index d99edd0c214b..53bb44a5969d 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index 7a69c3751d04..254f7e6edc96 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -266,7 +266,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 36bc2546deef..0330b287c8ca 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -126,7 +126,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index cdfc6bae47e6..ebce891aa88d 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index a6fba6e93cc2..69e30d46b1ab 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 8aa03dd2f492..5aa7caf7d4b0 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -203,7 +203,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index f53ff933dab5..57e01bbc3acc 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -143,7 +143,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
index 7a7421349903..769c3612f3bc 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -133,7 +133,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index d6cf84c4d73f..91dfa1af5392 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -230,7 +230,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index c72cd676bb9d..5237ce62982d 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index cf24a6ac08be..33f12b77d119 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -142,7 +142,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index ea6ec3cd4ce1..e1fd6793448d 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1037,7 +1037,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs
index ff745fb8c634..28babc164fa1 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index e29c3bd92ab7..f4eb5ec74fc0 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 774819500abb..3065aa784e40 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index a2f2a020ca01..924e7fba5a94 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index f559e8b80529..b5687bcc6220 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index c6845db92f21..e90cec4beeab 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index eba993bc6df9..39001954adab 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index 662ad9138d5a..40e377a738e5 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bf186426a730..a1331e30db52 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 55771aa8b908..62497a471010 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 29889efa16d7..7eff637ef4ab 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 65b685735f9d..37f064d7fd1e 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/User.cs
index 20b349a6dedf..b25565d980eb 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -265,7 +265,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index 85fe2d95bfe4..7b256f9ebe60 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index 53ea6867b306..fd95e1d63c14 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 6fa1afb780bb..71d5ea685aec 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Client/ApiClient.cs
index 200d5edb6387..58091fdfa71e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -31,7 +31,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -72,10 +71,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -501,7 +500,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 }
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/ApiResponse.cs
index f419649557f1..c1f57aacd690 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Category.cs
index 7f5cc435b4d1..c40164a04e4e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Category.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Name != null) {
                 // Name (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Order.cs
index 97cc5d2d96ee..72c797f4bf0d 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Order.cs
@@ -188,7 +188,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Pet.cs
index ed1b19130701..c4b9f01231cf 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Pet.cs
@@ -216,7 +216,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Tag.cs
index 0d025e3446bd..feaf2f9f98a7 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/Tag.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/User.cs
index 4aa50254f0ba..306c3e6cb3b6 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Model/User.cs
@@ -197,7 +197,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
index 65ae6b1f257f..45a4c47280d6 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -31,7 +31,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -72,10 +71,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -495,7 +494,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index db5b8c45b8f2..e55a21587236 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index ea9a0dc0f39c..533a81d9b0b3 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 99aff9d787c3..a2a1793c3b67 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -215,7 +215,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index f6d7f1cf5b60..244914ede066 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -164,7 +164,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index 7dec589c62d6..49b4a2e3a078 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index 12fef1561aa0..59d1eb66813c 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 15d96e2ee292..4c6717e8671a 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -131,7 +131,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 6757590569e8..367cffebf5f3 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 054b6cdd404f..ab500c64e0a7 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 7c148fc567b2..a99e707db885 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index c506c26dbb8a..308f9fd10e6a 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index a95d29e6aa0b..5062a8c34de7 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index bdb255710665..ac0672979a77 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index bf185fe10e60..239c14fc1a92 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -189,7 +189,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Cat.cs
index b7a2c073c0cf..075f957164be 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Cat.cs
@@ -132,7 +132,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -142,7 +142,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Category.cs
index b56dfc0c4828..823821fc3e83 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
index 75760311e7b2..ce2550c74a1e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -166,7 +166,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 66b8dbfc501f..6c7f38512827 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index b5cd8370cb9f..fa4d1f9e98f4 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index f3f19fce57f9..0ea24d160cef 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 9512789df4e4..ebfe7b04d755 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -127,7 +127,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 43886a5c8357..f1a47425f34e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Dog.cs
index 57a7e340dd4e..be9a5889ef9e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Dog.cs
@@ -135,7 +135,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -145,7 +145,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index f9918311cf5f..38561e69e644 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index 7a9834a78d18..9102c56cec8d 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index 0851264693b3..cbaef29ae70a 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -369,7 +369,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 373122a59235..6cf007da939f 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/File.cs
index 40dd973d3067..a4ef22ee1141 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c870be88db2f..3f45c47a6115 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 3108c8a86913..570e3de7f650 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 709031fd9398..e7ccfc43de0b 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 08306695ce09..d2993b2f7935 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -361,78 +361,78 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -447,13 +447,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 9d576878b233..9c5b047e85f0 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -150,7 +150,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 3c6298d7d8d2..2d4a1cd404f3 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index abb6777f0a75..67f7030ce8af 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 297e82fd9ba5..bdae3f577962 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/List.cs
index 7e4c1485e149..ec0286232f36 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index 57cc8110fbb8..3efdf1238452 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -138,7 +138,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index 64ca5484864e..f3bf0b27e67f 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -181,7 +181,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index c7684d040338..6e194e670356 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 38430dec6e6b..704488a0e32b 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index ec679f5c5bba..4467ab56f5d0 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 042125a808a5..d65f720a7540 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index 74b83092923f..5b0b4879e686 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 67847aa368e6..59474c83bf10 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 4eace322815d..288a511d8a01 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -173,7 +173,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index d99edd0c214b..53bb44a5969d 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index ccf32f99d282..1c5577f47c3e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -267,7 +267,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 36bc2546deef..0330b287c8ca 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -126,7 +126,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index cdfc6bae47e6..ebce891aa88d 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index a6fba6e93cc2..69e30d46b1ab 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 8aa03dd2f492..5aa7caf7d4b0 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -203,7 +203,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index f53ff933dab5..57e01bbc3acc 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -143,7 +143,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
index 7a7421349903..769c3612f3bc 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -133,7 +133,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index d6cf84c4d73f..91dfa1af5392 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -230,7 +230,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index c72cd676bb9d..5237ce62982d 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index cf24a6ac08be..33f12b77d119 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -142,7 +142,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index 596031f228fe..189456e91ea6 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1041,7 +1041,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Return.cs
index ff745fb8c634..28babc164fa1 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index e29c3bd92ab7..f4eb5ec74fc0 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 774819500abb..3065aa784e40 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index a2f2a020ca01..924e7fba5a94 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index f559e8b80529..b5687bcc6220 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index c6845db92f21..e90cec4beeab 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index eba993bc6df9..39001954adab 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index 662ad9138d5a..40e377a738e5 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bf186426a730..a1331e30db52 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 55771aa8b908..62497a471010 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 29889efa16d7..7eff637ef4ab 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 65b685735f9d..37f064d7fd1e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/User.cs
index 20b349a6dedf..b25565d980eb 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -265,7 +265,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index 85fe2d95bfe4..7b256f9ebe60 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index 53ea6867b306..fd95e1d63c14 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 6fa1afb780bb..71d5ea685aec 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
index 65ae6b1f257f..45a4c47280d6 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -31,7 +31,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -72,10 +71,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -495,7 +494,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index db5b8c45b8f2..e55a21587236 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index ea9a0dc0f39c..533a81d9b0b3 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 99aff9d787c3..a2a1793c3b67 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -215,7 +215,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index f6d7f1cf5b60..244914ede066 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -164,7 +164,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index 7dec589c62d6..49b4a2e3a078 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index 12fef1561aa0..59d1eb66813c 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 15d96e2ee292..4c6717e8671a 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -131,7 +131,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 6757590569e8..367cffebf5f3 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 054b6cdd404f..ab500c64e0a7 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 7c148fc567b2..a99e707db885 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index c506c26dbb8a..308f9fd10e6a 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index a95d29e6aa0b..5062a8c34de7 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index bdb255710665..ac0672979a77 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index bf185fe10e60..239c14fc1a92 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -189,7 +189,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Cat.cs
index b7a2c073c0cf..075f957164be 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Cat.cs
@@ -132,7 +132,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -142,7 +142,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Category.cs
index b56dfc0c4828..823821fc3e83 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
index 75760311e7b2..ce2550c74a1e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -166,7 +166,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 66b8dbfc501f..6c7f38512827 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index b5cd8370cb9f..fa4d1f9e98f4 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index f3f19fce57f9..0ea24d160cef 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 9512789df4e4..ebfe7b04d755 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -127,7 +127,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 43886a5c8357..f1a47425f34e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Dog.cs
index 57a7e340dd4e..be9a5889ef9e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Dog.cs
@@ -135,7 +135,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -145,7 +145,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index f9918311cf5f..38561e69e644 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index 7a9834a78d18..9102c56cec8d 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index 0851264693b3..cbaef29ae70a 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -369,7 +369,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 373122a59235..6cf007da939f 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/File.cs
index 40dd973d3067..a4ef22ee1141 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c870be88db2f..3f45c47a6115 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 3108c8a86913..570e3de7f650 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 709031fd9398..e7ccfc43de0b 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 08306695ce09..d2993b2f7935 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -361,78 +361,78 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -447,13 +447,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 9d576878b233..9c5b047e85f0 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -150,7 +150,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 3c6298d7d8d2..2d4a1cd404f3 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index abb6777f0a75..67f7030ce8af 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 297e82fd9ba5..bdae3f577962 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/List.cs
index 7e4c1485e149..ec0286232f36 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index 57cc8110fbb8..3efdf1238452 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -138,7 +138,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index 64ca5484864e..f3bf0b27e67f 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -181,7 +181,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index c7684d040338..6e194e670356 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 38430dec6e6b..704488a0e32b 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index ec679f5c5bba..4467ab56f5d0 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 042125a808a5..d65f720a7540 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index 74b83092923f..5b0b4879e686 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 67847aa368e6..59474c83bf10 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 4eace322815d..288a511d8a01 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -173,7 +173,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index d99edd0c214b..53bb44a5969d 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index ccf32f99d282..1c5577f47c3e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -267,7 +267,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 36bc2546deef..0330b287c8ca 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -126,7 +126,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index cdfc6bae47e6..ebce891aa88d 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index a6fba6e93cc2..69e30d46b1ab 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 8aa03dd2f492..5aa7caf7d4b0 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -203,7 +203,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index f53ff933dab5..57e01bbc3acc 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -143,7 +143,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
index 7a7421349903..769c3612f3bc 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -133,7 +133,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index d6cf84c4d73f..91dfa1af5392 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -230,7 +230,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index c72cd676bb9d..5237ce62982d 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index cf24a6ac08be..33f12b77d119 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -142,7 +142,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index 596031f228fe..189456e91ea6 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1041,7 +1041,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Return.cs
index ff745fb8c634..28babc164fa1 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index e29c3bd92ab7..f4eb5ec74fc0 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 774819500abb..3065aa784e40 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index a2f2a020ca01..924e7fba5a94 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index f559e8b80529..b5687bcc6220 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index c6845db92f21..e90cec4beeab 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index eba993bc6df9..39001954adab 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index 662ad9138d5a..40e377a738e5 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bf186426a730..a1331e30db52 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 55771aa8b908..62497a471010 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 29889efa16d7..7eff637ef4ab 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 65b685735f9d..37f064d7fd1e 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/User.cs
index 20b349a6dedf..b25565d980eb 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -265,7 +265,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index 85fe2d95bfe4..7b256f9ebe60 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index 53ea6867b306..fd95e1d63c14 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 6fa1afb780bb..71d5ea685aec 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs
index a8f6dea4407b..e39e44dc8d81 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -30,7 +30,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -71,10 +70,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -494,7 +493,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Activity.cs
index db5b8c45b8f2..e55a21587236 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Activity.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index ea9a0dc0f39c..533a81d9b0b3 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 99aff9d787c3..a2a1793c3b67 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -215,7 +215,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Animal.cs
index f6d7f1cf5b60..244914ede066 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Animal.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -164,7 +164,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs
index 7dec589c62d6..49b4a2e3a078 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Apple.cs
index 12fef1561aa0..59d1eb66813c 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Apple.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/AppleReq.cs
index 15d96e2ee292..4c6717e8671a 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -131,7 +131,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 6757590569e8..367cffebf5f3 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 054b6cdd404f..ab500c64e0a7 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayTest.cs
index 7c148fc567b2..a99e707db885 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Banana.cs
index c506c26dbb8a..308f9fd10e6a 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Banana.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/BananaReq.cs
index a95d29e6aa0b..5062a8c34de7 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/BasquePig.cs
index bdb255710665..ac0672979a77 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Capitalization.cs
index bf185fe10e60..239c14fc1a92 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -189,7 +189,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Cat.cs
index b7a2c073c0cf..075f957164be 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Cat.cs
@@ -132,7 +132,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -142,7 +142,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Category.cs
index b56dfc0c4828..823821fc3e83 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Category.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ChildCat.cs
index 75760311e7b2..ce2550c74a1e 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -166,7 +166,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ClassModel.cs
index 66b8dbfc501f..6c7f38512827 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index b5cd8370cb9f..fa4d1f9e98f4 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DanishPig.cs
index f3f19fce57f9..0ea24d160cef 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index e4660e563c78..41c78a93906b 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -126,7 +126,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 43886a5c8357..f1a47425f34e 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Dog.cs
index 57a7e340dd4e..be9a5889ef9e 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Dog.cs
@@ -135,7 +135,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -145,7 +145,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Drawing.cs
index f9918311cf5f..38561e69e644 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Drawing.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EnumArrays.cs
index 7a9834a78d18..9102c56cec8d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EnumTest.cs
index 0851264693b3..cbaef29ae70a 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -369,7 +369,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 373122a59235..6cf007da939f 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/File.cs
index 40dd973d3067..a4ef22ee1141 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/File.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c870be88db2f..3f45c47a6115 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Foo.cs
index 3108c8a86913..570e3de7f650 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Foo.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 709031fd9398..e7ccfc43de0b 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FormatTest.cs
index f036de12837b..cf8eeecd6f18 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -360,78 +360,78 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -446,13 +446,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 9d576878b233..9c5b047e85f0 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -150,7 +150,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 3c6298d7d8d2..2d4a1cd404f3 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index abb6777f0a75..67f7030ce8af 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 297e82fd9ba5..bdae3f577962 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/List.cs
index 7e4c1485e149..ec0286232f36 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/List.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index 57cc8110fbb8..3efdf1238452 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -138,7 +138,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MapTest.cs
index 64ca5484864e..f3bf0b27e67f 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MapTest.cs
@@ -181,7 +181,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index c7684d040338..6e194e670356 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 38430dec6e6b..704488a0e32b 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index ec679f5c5bba..4467ab56f5d0 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedSubId.cs
index 042125a808a5..d65f720a7540 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Model200Response.cs
index 74b83092923f..5b0b4879e686 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ModelClient.cs
index 67847aa368e6..59474c83bf10 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Name.cs
index 4eace322815d..288a511d8a01 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Name.cs
@@ -173,7 +173,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index d99edd0c214b..53bb44a5969d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NullableClass.cs
index 7a69c3751d04..254f7e6edc96 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -266,7 +266,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 36bc2546deef..0330b287c8ca 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -126,7 +126,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NumberOnly.cs
index cdfc6bae47e6..ebce891aa88d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index a6fba6e93cc2..69e30d46b1ab 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Order.cs
index 6b8d5b268364..390c514aa0e7 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Order.cs
@@ -203,7 +203,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/OuterComposite.cs
index f53ff933dab5..57e01bbc3acc 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -143,7 +143,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ParentPet.cs
index 7a7421349903..769c3612f3bc 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -133,7 +133,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs
index d6cf84c4d73f..91dfa1af5392 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs
@@ -230,7 +230,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index c72cd676bb9d..5237ce62982d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index cf24a6ac08be..33f12b77d119 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -142,7 +142,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RequiredClass.cs
index ea6ec3cd4ce1..e1fd6793448d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1037,7 +1037,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Return.cs
index ff745fb8c634..28babc164fa1 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Return.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index e29c3bd92ab7..f4eb5ec74fc0 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 774819500abb..3065aa784e40 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index a2f2a020ca01..924e7fba5a94 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ShapeInterface.cs
index f559e8b80529..b5687bcc6220 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index c6845db92f21..e90cec4beeab 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/SpecialModelName.cs
index eba993bc6df9..39001954adab 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs
index 662ad9138d5a..40e377a738e5 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bf186426a730..a1331e30db52 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 55771aa8b908..62497a471010 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 29889efa16d7..7eff637ef4ab 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 65b685735f9d..37f064d7fd1e 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/User.cs
index 20b349a6dedf..b25565d980eb 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/User.cs
@@ -265,7 +265,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Whale.cs
index 85fe2d95bfe4..7b256f9ebe60 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Whale.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Zebra.cs
index 53ea6867b306..fd95e1d63c14 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/Zebra.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 6fa1afb780bb..71d5ea685aec 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Client/ApiClient.cs
index 7dce1917d437..798f6d5833bd 100644
--- a/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -29,7 +29,6 @@
 using RestSharpMethod = RestSharp.Method;
 using FileIO = System.IO.File;
 using Polly;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -70,10 +69,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -478,7 +477,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Model/Env.cs b/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Model/Env.cs
index dc7827b7eee4..195cbf166045 100644
--- a/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Model/Env.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Model/Env.cs
@@ -119,7 +119,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Model/PropertyNameMapping.cs b/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Model/PropertyNameMapping.cs
index 42c335e3e0f1..aa964c6b63e9 100644
--- a/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Model/PropertyNameMapping.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Model/PropertyNameMapping.cs
@@ -173,7 +173,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
index a8f6dea4407b..e39e44dc8d81 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -30,7 +30,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -71,10 +70,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -494,7 +493,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index a1de5af6e0d5..9b95ac93378d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 278fc42e1673..83bda986d8ea 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index b5bfc54646f2..e28e454ee3df 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -203,7 +203,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index 5bebc2849244..08fcd8006078 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -149,7 +149,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index ed83e9c9079a..e0ce288341da 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -134,7 +134,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index d035733fcea3..2791eb10c38e 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 15d96e2ee292..4c6717e8671a 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -131,7 +131,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 5c531d91018f..3eca3c63120e 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index d662e04766b8..c3ee3f9f1eda 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 2b0ed0411c4f..1f007a835a0d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index 7100a90faf0d..0bbac6d6efec 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -108,7 +108,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index a95d29e6aa0b..5062a8c34de7 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index 9c7a372b8bad..a0043566e0bb 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index bc116f13a11b..2130cea72f75 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -177,7 +177,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Cat.cs
index d14a4e387721..28affd8ba43b 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Cat.cs
@@ -117,7 +117,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -127,7 +127,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Category.cs
index 4e9591df4cc9..8fa4fd029965 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -131,7 +131,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
index 116d3f85c94d..b2fdd593200d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -151,7 +151,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 9b1e093e4252..b27df528bd34 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 2feaeae90e16..d437d43637e2 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
index 96416b82ded0..4031a2614240 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/CopyActivity.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -156,7 +156,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index ca40481c94f3..ae9749fbbbb3 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 8907f03d78ca..58d6a9e283c9 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -114,7 +114,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 42a6c8159287..deb1c6198fee 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
index 837a94858dcc..1c9c7b10830e 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Descendant1.cs
@@ -125,7 +125,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -135,7 +135,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
index 570c05159b93..710166dbc89c 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Descendant2.cs
@@ -125,7 +125,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -135,7 +135,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Dog.cs
index f257934b9b8c..e4b9da83cc4e 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Dog.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -130,7 +130,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index f9918311cf5f..38561e69e644 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
index d657ab5587ce..d9f067bdcdc4 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -134,7 +134,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index 7dd8b1c9e01b..7183da42e4ae 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -159,7 +159,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index 5d6b305bb33b..dd4428b0b2ca 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -354,7 +354,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 8d90f3fd5941..f30d1a107bc9 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/File.cs
index da3570ddb713..7a8d20be2f9a 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -112,7 +112,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 36150e673d71..d1b7bec88be8 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 9691b4848101..7d665273f1d1 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -112,7 +112,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 51f765d2b501..edc0e5b28991 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 7f8d2409a609..59c41b91f3d5 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -441,114 +441,114 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32Range > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32Range < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64Positive < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64Negative > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusive < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusive <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -563,13 +563,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 54208034faf0..fba17ad233c2 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -125,7 +125,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -135,7 +135,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 712d33733e8d..952e3eac26ec 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -137,7 +137,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index 79bcfc38ed5a..b168c0bce8fd 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index fd9d2b3dd793..54032ea8fcf2 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -200,7 +200,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 297e82fd9ba5..bdae3f577962 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/List.cs
index a1d2b4e0dd8f..08f6c0b17d8d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index 15b6f0eabba9..eb7c8d83ab6d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -126,7 +126,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index be17172c3156..2c6e55164a37 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -169,7 +169,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 4603c4221102..e2a764685736 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 072531765047..e632b8953e24 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 55857c0d1c5f..67c4cb23832b 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 4ef46d89af8b..3ed77c1f8e11 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index 40318b19ff80..501551952555 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 139a8d5137f9..6d633ca17241 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 8c7eab2b0f90..e08d49c41426 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -158,7 +158,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 3ffceba8816f..3aa0c301e182 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -131,7 +131,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index 7a69c3751d04..254f7e6edc96 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -266,7 +266,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index a03996310c5a..1d417c77122e 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -114,7 +114,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index 0c5015ded6e4..b616ad0dbadd 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index 5d1b92de8fe4..4db206957028 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -150,7 +150,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Order.cs
index ae9d7efd80b2..49da7dcc7f35 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -191,7 +191,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index 3512652479c8..838ce576a2dc 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -131,7 +131,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
index 4d15a2a962f9..805eb998332d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -108,7 +108,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -118,7 +118,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index aaac5180f51c..fba4e510eac7 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -215,7 +215,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 14728fe2a11a..e9055d7ba635 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 6f25c6544426..0bd541a07f5a 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -130,7 +130,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index 403137a821e6..2d8dbf2d3084 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1022,7 +1022,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Result.cs
index 0e98c9e6adda..d3a2268d0086 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Result.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Return.cs
index aeb4413b4b37..aadd35036b1f 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index cff11245e73c..4771dbe132bd 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index e523dc4ca1ef..a97b6c4371bb 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index 2594a92e33a7..f42bab7e3b12 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index 67cd6f93c11b..87cdcdd5e8cc 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 3ee8519261ad..05f9045d3dba 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index 94d720398f89..cd46a83c1b07 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index 57eaeca6d844..aaa9ba9a7951 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index e95419b30752..53699f33b504 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 9ed09a2e8c59..36634fc656bb 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -111,7 +111,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
index 86a753ca9f9c..76e8effd020f 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -164,7 +164,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 29889efa16d7..7eff637ef4ab 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
index 59e120b99b4e..5660dad5f745 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TestResult.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 0324ee2cb42a..b0f16d30da87 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/User.cs
index 9a38afa62526..7f6374a905de 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -253,7 +253,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index b5c2dc8e894f..b033982816ac 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -141,7 +141,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index 53ea6867b306..fd95e1d63c14 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 690fb260db2c..dcfbee3674da 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -127,7 +127,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiClient.cs
index 7eeae6d57dbd..5b96bec3efc7 100644
--- a/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -29,7 +29,6 @@
 using RestSharpMethod = RestSharp.Method;
 using FileIO = System.IO.File;
 using Polly;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -70,10 +69,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -478,7 +477,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs b/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
index 17f80d194604..d04f0118ef89 100644
--- a/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Model/NowGet200Response.cs
@@ -83,7 +83,7 @@ public virtual string ToJson()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Client/ApiClient.cs
index f7d52cf92773..0e089252bb38 100644
--- a/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -30,7 +30,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -71,10 +70,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -494,7 +493,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Category.cs
index 5afa92d0e516..e7d744b8f34a 100644
--- a/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Category.cs
@@ -82,7 +82,7 @@ public virtual string ToJson()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Name != null) {
                 // Name (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Pet.cs
index ac900b44a527..28fe617ad10d 100644
--- a/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Pet.cs
@@ -164,7 +164,7 @@ public virtual string ToJson()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Tag.cs
index 294ae82c1820..39c105ac9fc3 100644
--- a/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Model/Tag.cs
@@ -82,7 +82,7 @@ public virtual string ToJson()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs
index a8f6dea4407b..e39e44dc8d81 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -30,7 +30,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -71,10 +70,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -494,7 +493,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Activity.cs
index db5b8c45b8f2..e55a21587236 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Activity.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index ea9a0dc0f39c..533a81d9b0b3 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 99aff9d787c3..a2a1793c3b67 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -215,7 +215,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Animal.cs
index f6d7f1cf5b60..244914ede066 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Animal.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -164,7 +164,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs
index 7dec589c62d6..49b4a2e3a078 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Apple.cs
index 12fef1561aa0..59d1eb66813c 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Apple.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/AppleReq.cs
index 15d96e2ee292..4c6717e8671a 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -131,7 +131,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 6757590569e8..367cffebf5f3 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 054b6cdd404f..ab500c64e0a7 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayTest.cs
index 7c148fc567b2..a99e707db885 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Banana.cs
index c506c26dbb8a..308f9fd10e6a 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Banana.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/BananaReq.cs
index a95d29e6aa0b..5062a8c34de7 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/BasquePig.cs
index bdb255710665..ac0672979a77 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Capitalization.cs
index bf185fe10e60..239c14fc1a92 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -189,7 +189,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Cat.cs
index b7a2c073c0cf..075f957164be 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Cat.cs
@@ -132,7 +132,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -142,7 +142,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Category.cs
index b56dfc0c4828..823821fc3e83 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Category.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ChildCat.cs
index 75760311e7b2..ce2550c74a1e 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -166,7 +166,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ClassModel.cs
index 66b8dbfc501f..6c7f38512827 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index b5cd8370cb9f..fa4d1f9e98f4 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DanishPig.cs
index f3f19fce57f9..0ea24d160cef 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index e4660e563c78..41c78a93906b 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -126,7 +126,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 43886a5c8357..f1a47425f34e 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Dog.cs
index 57a7e340dd4e..be9a5889ef9e 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Dog.cs
@@ -135,7 +135,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -145,7 +145,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Drawing.cs
index f9918311cf5f..38561e69e644 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Drawing.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EnumArrays.cs
index 7a9834a78d18..9102c56cec8d 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EnumTest.cs
index 0851264693b3..cbaef29ae70a 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -369,7 +369,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 373122a59235..6cf007da939f 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/File.cs
index 40dd973d3067..a4ef22ee1141 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/File.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c870be88db2f..3f45c47a6115 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Foo.cs
index 3108c8a86913..570e3de7f650 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Foo.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 709031fd9398..e7ccfc43de0b 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FormatTest.cs
index f036de12837b..cf8eeecd6f18 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -360,78 +360,78 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -446,13 +446,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 9d576878b233..9c5b047e85f0 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -150,7 +150,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 3c6298d7d8d2..2d4a1cd404f3 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index abb6777f0a75..67f7030ce8af 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 297e82fd9ba5..bdae3f577962 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/List.cs
index 7e4c1485e149..ec0286232f36 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/List.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index 57cc8110fbb8..3efdf1238452 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -138,7 +138,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MapTest.cs
index 64ca5484864e..f3bf0b27e67f 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MapTest.cs
@@ -181,7 +181,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index c7684d040338..6e194e670356 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 38430dec6e6b..704488a0e32b 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index ec679f5c5bba..4467ab56f5d0 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedSubId.cs
index 042125a808a5..d65f720a7540 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Model200Response.cs
index 74b83092923f..5b0b4879e686 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ModelClient.cs
index 67847aa368e6..59474c83bf10 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Name.cs
index 4eace322815d..288a511d8a01 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Name.cs
@@ -173,7 +173,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index d99edd0c214b..53bb44a5969d 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NullableClass.cs
index 7a69c3751d04..254f7e6edc96 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -266,7 +266,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 36bc2546deef..0330b287c8ca 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -126,7 +126,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NumberOnly.cs
index cdfc6bae47e6..ebce891aa88d 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index a6fba6e93cc2..69e30d46b1ab 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Order.cs
index 6b8d5b268364..390c514aa0e7 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Order.cs
@@ -203,7 +203,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/OuterComposite.cs
index f53ff933dab5..57e01bbc3acc 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -143,7 +143,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ParentPet.cs
index 7a7421349903..769c3612f3bc 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -133,7 +133,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs
index d6cf84c4d73f..91dfa1af5392 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Pet.cs
@@ -230,7 +230,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index c72cd676bb9d..5237ce62982d 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index cf24a6ac08be..33f12b77d119 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -142,7 +142,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RequiredClass.cs
index ea6ec3cd4ce1..e1fd6793448d 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1037,7 +1037,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Return.cs
index ff745fb8c634..28babc164fa1 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Return.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index e29c3bd92ab7..f4eb5ec74fc0 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 774819500abb..3065aa784e40 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index a2f2a020ca01..924e7fba5a94 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ShapeInterface.cs
index f559e8b80529..b5687bcc6220 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index c6845db92f21..e90cec4beeab 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/SpecialModelName.cs
index eba993bc6df9..39001954adab 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs
index 662ad9138d5a..40e377a738e5 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Tag.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bf186426a730..a1331e30db52 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 55771aa8b908..62497a471010 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 29889efa16d7..7eff637ef4ab 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 65b685735f9d..37f064d7fd1e 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/User.cs
index 20b349a6dedf..b25565d980eb 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/User.cs
@@ -265,7 +265,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Whale.cs
index 85fe2d95bfe4..7b256f9ebe60 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Whale.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Zebra.cs
index 53ea6867b306..fd95e1d63c14 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/Zebra.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 6fa1afb780bb..71d5ea685aec 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Client/ApiClient.cs
index 65ae6b1f257f..45a4c47280d6 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -31,7 +31,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -72,10 +71,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -495,7 +494,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Activity.cs
index ac0413d8c2a5..3988c6b4ff87 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Activity.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index 5502a36a84c0..8413b1785bc2 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -180,7 +180,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 5098c3a3b6f9..75567736f1d1 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -391,7 +391,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Animal.cs
index b6a28a7e3c9c..bffacf7045b8 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Animal.cs
@@ -188,7 +188,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -198,7 +198,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ApiResponse.cs
index 4e4ea7a29af6..c65f4308a1f4 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -212,7 +212,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Apple.cs
index 1b803b3cd512..0622cb83f530 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Apple.cs
@@ -215,7 +215,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/AppleReq.cs
index 3c6e86b9dd16..4668b38b7141 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index deb990f8abe8..197d4c4a06a9 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index c139a3fb7d51..e9d0a5a2d7ef 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayTest.cs
index ca1f61b2a2b3..e5d164fbc7b9 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -215,7 +215,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Banana.cs
index 8fa191bb07d9..81e66ff0f68a 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Banana.cs
@@ -142,7 +142,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/BananaReq.cs
index c77084eec25a..a7d665be7367 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/BasquePig.cs
index b3acb5950bee..ddca40494c03 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Capitalization.cs
index f70667655f71..d9a936dbbb25 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -321,7 +321,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Cat.cs
index eda5df130c9a..b45f6444bff1 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Cat.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -164,7 +164,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Category.cs
index 4a38856efa12..80dfeba682ee 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Category.cs
@@ -186,7 +186,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ChildCat.cs
index 7405339b1bc5..16eb0caf8d56 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -198,7 +198,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -208,7 +208,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ClassModel.cs
index 9d569f2b0530..5043fe970b49 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index 40bc0fa67042..284cf7eaef6f 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -190,7 +190,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/CopyActivity.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/CopyActivity.cs
index 8484b5f0c9cb..a95f3f7cb1c2 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/CopyActivity.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/CopyActivity.cs
@@ -199,7 +199,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -209,7 +209,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DanishPig.cs
index 583ace694ebd..0b231ef405c6 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 3923331b6697..73a8421a01e0 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 8be8ef969351..c87d2e366821 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Descendant1.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Descendant1.cs
index fc33e9ca0177..ce905f87d0ec 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Descendant1.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Descendant1.cs
@@ -158,7 +158,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -168,7 +168,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Descendant2.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Descendant2.cs
index 856c7370eda4..e63822cdb6c1 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Descendant2.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Descendant2.cs
@@ -158,7 +158,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -168,7 +168,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Dog.cs
index bcbbf8db01a4..d942a33904b4 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Dog.cs
@@ -157,7 +157,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -167,7 +167,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Drawing.cs
index d7fa71ed6efe..5f9f9d4f4546 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Drawing.cs
@@ -250,7 +250,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EntityBase.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EntityBase.cs
index cccad486fa39..30e11a7851d1 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EntityBase.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EntityBase.cs
@@ -157,7 +157,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -167,7 +167,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EnumArrays.cs
index aa75b5a918b7..99ab3de5b9d3 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -217,7 +217,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EnumTest.cs
index 6158d41ee7cc..0819b412269b 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -581,7 +581,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 2b64977c4cb8..94fa91542090 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -190,7 +190,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/File.cs
index 892a6c6adbd2..78a402ed5f9b 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/File.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index 45e88f83a8cd..3715f1bab8ec 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -180,7 +180,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Foo.cs
index 7558351cafaa..05dbdea1c073 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Foo.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 41b19f5518a6..fdb696fdfcb6 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FormatTest.cs
index 09fae29f3c7e..34677b43b683 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -1053,114 +1053,114 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // Int32Range (int) maximum
             if (this.Int32Range > (int)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value less than or equal to 2147483647.", new [] { "Int32Range" });
             }
 
             // Int32Range (int) minimum
             if (this.Int32Range < (int)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32Range, must be a value greater than or equal to -2147483648.", new [] { "Int32Range" });
             }
 
             // Int64Positive (long) minimum
             if (this.Int64Positive < (long)2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Positive, must be a value greater than or equal to 2147483648.", new [] { "Int64Positive" });
             }
 
             // Int64Negative (long) maximum
             if (this.Int64Negative > (long)-2147483649)
             {
-                yield return new ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64Negative, must be a value less than or equal to -2147483649.", new [] { "Int64Negative" });
             }
 
             // Int64PositiveExclusive (long) minimum
             if (this.Int64PositiveExclusive < (long)2147483647)
             {
-                yield return new ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64PositiveExclusive, must be a value greater than 2147483647.", new [] { "Int64PositiveExclusive" });
             }
 
             // Int64NegativeExclusive (long) maximum
             if (this.Int64NegativeExclusive <= (long)-2147483648)
             {
-                yield return new ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int64NegativeExclusive, must be a value less than -2147483648.", new [] { "Int64NegativeExclusive" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -1175,13 +1175,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index ab2e27672ef1..01d5adb8a9c0 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -158,7 +158,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -168,7 +168,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 3c6298d7d8d2..2d4a1cd404f3 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index 7ae4ce9d40a8..2a99b92ae82f 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
index 1b60d9480cee..f489b1cf21e9 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/InjectedVendorExtensionsTest.cs
@@ -256,7 +256,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index a552ae664641..2967b4df52c8 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -175,7 +175,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/List.cs
index 9bbe350996dc..20b5263bfc20 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/List.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index aca243cc3c53..ddfb8b005d27 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -170,7 +170,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MapTest.cs
index cfbb15806103..54aeff9f3476 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MapTest.cs
@@ -269,7 +269,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index 6028f2e54302..b0328291dc88 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 13d0df55cac3..02fec01358b7 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index 187bca7b07fb..702647088805 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -250,7 +250,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedSubId.cs
index 4aa98913af00..c4c280aeb362 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Model200Response.cs
index 482a70ef3e78..0ad2401f833f 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -177,7 +177,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ModelClient.cs
index cbc1c7fe6403..f208edca1d94 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Name.cs
index e7055534004e..12367e994fe7 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Name.cs
@@ -213,7 +213,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index 227922a8fa19..58c0099072fd 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -182,7 +182,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NullableClass.cs
index feab5ee958b2..2870f0a78ed2 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -531,7 +531,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 694d2c01e0bb..a359a0dcebaf 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -148,7 +148,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NumberOnly.cs
index c5143c1a5a62..052a393d4c3a 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index 2fe23672496a..8b8af740411b 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -250,7 +250,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Order.cs
index ff5a01987383..ea0d7a85e60c 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Order.cs
@@ -332,7 +332,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/OuterComposite.cs
index 406c8c52f0e8..907282bc3748 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -209,7 +209,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ParentPet.cs
index 7a7421349903..769c3612f3bc 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -133,7 +133,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Pet.cs
index 8b1bd25ba47d..b62f26d1a876 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Pet.cs
@@ -356,7 +356,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index 75995ecfa2d4..4ad6a38d0a4d 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index 848fdcf18429..f68fca7b1ba1 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -164,7 +164,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RequiredClass.cs
index db4dbf576bcc..54a685a7d97f 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1953,7 +1953,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Result.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Result.cs
index 1fd86b15b269..13c430076481 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Result.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Result.cs
@@ -218,7 +218,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Return.cs
index 997837d01848..96ffa099c3f3 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Return.cs
@@ -257,7 +257,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index 0077a271cc21..c0d2177c9bae 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -180,7 +180,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 02e0468d8ca9..39da415319ec 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index f5bd010184df..308670ce4766 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -190,7 +190,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ShapeInterface.cs
index f4d40aed5d6b..e81cc705c330 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index 0bed8c231307..5b386bf51fd3 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -190,7 +190,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/SpecialModelName.cs
index e0408e63a083..8807a195a7de 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -177,7 +177,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Tag.cs
index 877c8249222f..bc702ab87ccb 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Tag.cs
@@ -177,7 +177,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index 65654edbc81e..abc5b6d6cc41 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 1bc3c30c0de6..609bc679403b 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestDescendants.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestDescendants.cs
index 155e88f28815..5d80b0a4ee83 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestDescendants.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestDescendants.cs
@@ -207,7 +207,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -217,7 +217,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 8457f79061f7..fd6f15101c9e 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -145,7 +145,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestResult.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestResult.cs
index b8ebba133514..41f04955a8f1 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestResult.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TestResult.cs
@@ -216,7 +216,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TriangleInterface.cs
index f37472cadd4c..2e100dada891 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/User.cs
index 203166eeeec3..ad9744d94075 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/User.cs
@@ -529,7 +529,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Whale.cs
index f5e732af315a..4593f685eea4 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Whale.cs
@@ -218,7 +218,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Zebra.cs
index de06d726d8f7..b2fc9b8bb33e 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/Zebra.cs
@@ -213,7 +213,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 9804d01afe37..85b62870aca7 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -163,7 +163,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
index 65ae6b1f257f..45a4c47280d6 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -31,7 +31,6 @@
 using FileIO = System.IO.File;
 using Polly;
 using Org.OpenAPITools.Client.Auth;
-using Org.OpenAPITools.Model;
 
 namespace Org.OpenAPITools.Client
 {
@@ -72,10 +71,10 @@ public CustomJsonCodec(JsonSerializerSettings serializerSettings, IReadableConfi
         /// <returns>A JSON string.</returns>
         public string Serialize(object obj)
         {
-            if (obj != null && obj is AbstractOpenAPISchema)
+            if (obj != null && obj is Org.OpenAPITools.Model.AbstractOpenAPISchema)
             {
                 // the object to be serialized is an oneOf/anyOf schema
-                return ((AbstractOpenAPISchema)obj).ToJson();
+                return ((Org.OpenAPITools.Model.AbstractOpenAPISchema)obj).ToJson();
             }
             else
             {
@@ -495,7 +494,7 @@ private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<Rest
                 RestResponse<T> response = await getResponse(client).ConfigureAwait(false);
 
                 // if the response type is oneOf/anyOf, call FromJSON to deserialize the data
-                if (typeof(AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
+                if (typeof(Org.OpenAPITools.Model.AbstractOpenAPISchema).IsAssignableFrom(typeof(T)))
                 {
                     try
                     {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs
index db5b8c45b8f2..e55a21587236 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Activity.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
index ea9a0dc0f39c..533a81d9b0b3 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ActivityOutputElementRepresentation.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
index 99aff9d787c3..a2a1793c3b67 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/AdditionalPropertiesClass.cs
@@ -215,7 +215,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs
index f6d7f1cf5b60..244914ede066 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Animal.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -164,7 +164,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
index 7dec589c62d6..49b4a2e3a078 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ApiResponse.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs
index 12fef1561aa0..59d1eb66813c 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Apple.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.Cultivar != null) {
                 // Cultivar (string) pattern
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
index 15d96e2ee292..4c6717e8671a 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/AppleReq.cs
@@ -131,7 +131,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
index 6757590569e8..367cffebf5f3 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
index 054b6cdd404f..ab500c64e0a7 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayOfNumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
index 7c148fc567b2..a99e707db885 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ArrayTest.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs
index c506c26dbb8a..308f9fd10e6a 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Banana.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
index a95d29e6aa0b..5062a8c34de7 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/BananaReq.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
index bdb255710665..ac0672979a77 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/BasquePig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
index bf185fe10e60..239c14fc1a92 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Capitalization.cs
@@ -189,7 +189,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Cat.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Cat.cs
index b7a2c073c0cf..075f957164be 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Cat.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Cat.cs
@@ -132,7 +132,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -142,7 +142,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs
index b56dfc0c4828..823821fc3e83 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Category.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
index 75760311e7b2..ce2550c74a1e 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ChildCat.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -166,7 +166,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
index 66b8dbfc501f..6c7f38512827 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ClassModel.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
index b5cd8370cb9f..fa4d1f9e98f4 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ComplexQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
index f3f19fce57f9..0ea24d160cef 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DanishPig.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
index 9512789df4e4..ebfe7b04d755 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DateOnlyClass.cs
@@ -127,7 +127,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
index 43886a5c8357..f1a47425f34e 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/DeprecatedObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Dog.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Dog.cs
index 57a7e340dd4e..be9a5889ef9e 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Dog.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Dog.cs
@@ -135,7 +135,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -145,7 +145,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
index f9918311cf5f..38561e69e644 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Drawing.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
index 7a9834a78d18..9102c56cec8d 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumArrays.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
index 0851264693b3..cbaef29ae70a 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EnumTest.cs
@@ -369,7 +369,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
index 373122a59235..6cf007da939f 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/EquilateralTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs
index 40dd973d3067..a4ef22ee1141 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/File.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
index c870be88db2f..3f45c47a6115 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FileSchemaTestClass.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs
index 3108c8a86913..570e3de7f650 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Foo.cs
@@ -124,7 +124,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
index 709031fd9398..e7ccfc43de0b 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FooGetDefaultResponse.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
index 08306695ce09..d2993b2f7935 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/FormatTest.cs
@@ -361,78 +361,78 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             // Integer (int) maximum
             if (this.Integer > (int)100)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value less than or equal to 100.", new [] { "Integer" });
             }
 
             // Integer (int) minimum
             if (this.Integer < (int)10)
             {
-                yield return new ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Integer, must be a value greater than or equal to 10.", new [] { "Integer" });
             }
 
             // Int32 (int) maximum
             if (this.Int32 > (int)200)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value less than or equal to 200.", new [] { "Int32" });
             }
 
             // Int32 (int) minimum
             if (this.Int32 < (int)20)
             {
-                yield return new ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Int32, must be a value greater than or equal to 20.", new [] { "Int32" });
             }
 
             // UnsignedInteger (uint) maximum
             if (this.UnsignedInteger > (uint)200)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value less than or equal to 200.", new [] { "UnsignedInteger" });
             }
 
             // UnsignedInteger (uint) minimum
             if (this.UnsignedInteger < (uint)20)
             {
-                yield return new ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for UnsignedInteger, must be a value greater than or equal to 20.", new [] { "UnsignedInteger" });
             }
 
             // Number (decimal) maximum
             if (this.Number > (decimal)543.2)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value less than or equal to 543.2.", new [] { "Number" });
             }
 
             // Number (decimal) minimum
             if (this.Number < (decimal)32.1)
             {
-                yield return new ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Number, must be a value greater than or equal to 32.1.", new [] { "Number" });
             }
 
             // Float (float) maximum
             if (this.Float > (float)987.6)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value less than or equal to 987.6.", new [] { "Float" });
             }
 
             // Float (float) minimum
             if (this.Float < (float)54.3)
             {
-                yield return new ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Float, must be a value greater than or equal to 54.3.", new [] { "Float" });
             }
 
             // Double (double) maximum
             if (this.Double > (double)123.4)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value less than or equal to 123.4.", new [] { "Double" });
             }
 
             // Double (double) minimum
             if (this.Double < (double)67.8)
             {
-                yield return new ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Double, must be a value greater than or equal to 67.8.", new [] { "Double" });
             }
 
             if (this.String != null) {
@@ -447,13 +447,13 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
             // Password (string) maxLength
             if (this.Password != null && this.Password.Length > 64)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be less than 64.", new [] { "Password" });
             }
 
             // Password (string) minLength
             if (this.Password != null && this.Password.Length < 10)
             {
-                yield return new ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
+                yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Password, length must be greater than 10.", new [] { "Password" });
             }
 
             if (this.PatternWithDigits != null) {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
index 9d576878b233..9c5b047e85f0 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/GrandparentAnimal.cs
@@ -140,7 +140,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -150,7 +150,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
index 3c6298d7d8d2..2d4a1cd404f3 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/HasOnlyReadOnly.cs
@@ -149,7 +149,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
index abb6777f0a75..67f7030ce8af 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/HealthCheckResult.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
index 297e82fd9ba5..bdae3f577962 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/IsoscelesTriangle.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs
index 7e4c1485e149..ec0286232f36 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/List.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
index 57cc8110fbb8..3efdf1238452 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/LiteralStringClass.cs
@@ -138,7 +138,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
index 64ca5484864e..f3bf0b27e67f 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MapTest.cs
@@ -181,7 +181,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
index c7684d040338..6e194e670356 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedAnyOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
index 38430dec6e6b..704488a0e32b 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedOneOf.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
index ec679f5c5bba..4467ab56f5d0 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedPropertiesAndAdditionalPropertiesClass.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             if (this.UuidWithPattern != null) {
                 // UuidWithPattern (Guid) pattern
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
index 042125a808a5..d65f720a7540 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/MixedSubId.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
index 74b83092923f..5b0b4879e686 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Model200Response.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
index 67847aa368e6..59474c83bf10 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs
index 4eace322815d..288a511d8a01 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Name.cs
@@ -173,7 +173,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
index d99edd0c214b..53bb44a5969d 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NotificationtestGetElementsV1ResponseMPayload.cs
@@ -146,7 +146,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
index ccf32f99d282..1c5577f47c3e 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableClass.cs
@@ -267,7 +267,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
index 36bc2546deef..0330b287c8ca 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NullableGuidClass.cs
@@ -126,7 +126,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
index cdfc6bae47e6..ebce891aa88d 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/NumberOnly.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
index a6fba6e93cc2..69e30d46b1ab 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ObjectWithDeprecatedFields.cs
@@ -162,7 +162,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs
index 8aa03dd2f492..5aa7caf7d4b0 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Order.cs
@@ -203,7 +203,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
index f53ff933dab5..57e01bbc3acc 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/OuterComposite.cs
@@ -143,7 +143,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
index 7a7421349903..769c3612f3bc 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ParentPet.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             return this.BaseValidate(validationContext);
         }
@@ -133,7 +133,7 @@ IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext vali
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        protected IEnumerable<ValidationResult> BaseValidate(ValidationContext validationContext)
+        protected IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> BaseValidate(ValidationContext validationContext)
         {
             foreach (var x in base.BaseValidate(validationContext))
             {
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs
index d6cf84c4d73f..91dfa1af5392 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Pet.cs
@@ -230,7 +230,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
index c72cd676bb9d..5237ce62982d 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/QuadrilateralInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
index cf24a6ac08be..33f12b77d119 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ReadOnlyFirst.cs
@@ -142,7 +142,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
index 596031f228fe..189456e91ea6 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RequiredClass.cs
@@ -1041,7 +1041,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs
index ff745fb8c634..28babc164fa1 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Return.cs
@@ -120,7 +120,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
index e29c3bd92ab7..f4eb5ec74fc0 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHash.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
index 774819500abb..3065aa784e40 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/RolesReportsHashRole.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
index a2f2a020ca01..924e7fba5a94 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ScaleneTriangle.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
index f559e8b80529..b5687bcc6220 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ShapeInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
index c6845db92f21..e90cec4beeab 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/SimpleQuadrilateral.cs
@@ -154,7 +154,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index eba993bc6df9..39001954adab 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs
index 662ad9138d5a..40e377a738e5 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Tag.cs
@@ -133,7 +133,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
index bf186426a730..a1331e30db52 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
index 55771aa8b908..62497a471010 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
index 29889efa16d7..7eff637ef4ab 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TestInlineFreeformAdditionalPropertiesRequest.cs
@@ -123,7 +123,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
index 65b685735f9d..37f064d7fd1e 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/TriangleInterface.cs
@@ -136,7 +136,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs
index 20b349a6dedf..b25565d980eb 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/User.cs
@@ -265,7 +265,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs
index 85fe2d95bfe4..7b256f9ebe60 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Whale.cs
@@ -156,7 +156,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
index 53ea6867b306..fd95e1d63c14 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/Zebra.cs
@@ -171,7 +171,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
index 6fa1afb780bb..71d5ea685aec 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Model/ZeroBasedEnumClass.cs
@@ -139,7 +139,7 @@ public override int GetHashCode()
         /// </summary>
         /// <param name="validationContext">Validation context</param>
         /// <returns>Validation Result</returns>
-        IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
+        IEnumerable<System.ComponentModel.DataAnnotations.ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
         {
             yield break;
         }