diff --git a/modules/openapi-generator/src/main/resources/csharp/ClientUtils.mustache b/modules/openapi-generator/src/main/resources/csharp/ClientUtils.mustache
index 4127944c4b0e..d5da856eadea 100644
--- a/modules/openapi-generator/src/main/resources/csharp/ClientUtils.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/ClientUtils.mustache
@@ -221,8 +221,7 @@ namespace {{packageName}}.Client
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -231,10 +230,7 @@ namespace {{packageName}}.Client
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
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 975eb0eeb512..a68c968d5296 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
@@ -409,6 +409,30 @@ public void testUserAgentIsNotUrlEncoded() throws IOException {
         }
     }
 
+    @Test
+    public void testSelectHeaderAcceptKeepsAllTypesJsonFirst() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/petstore.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);
+
+        Map<String, File> files = defaultGenerator.generate().stream()
+                .collect(Collectors.toMap(File::getPath, Function.identity()));
+
+        File clientUtils = files
+                .get(Paths.get(output.getAbsolutePath(), "src", "Org.OpenAPITools", "Client", "ClientUtils.cs").toString());
+        assertNotNull(clientUtils);
+        assertFileContains(clientUtils.toPath(), "accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1)");
+        assertFileNotContains(clientUtils.toPath(), "return \"application/json\";");
+    }
+
     @Test
     public void test31specAdditionalPropertiesOfOneOf() throws IOException {
         // for https://github.com/OpenAPITools/openapi-generator/pull/18772
diff --git a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Client/ClientUtils.cs
index e3787b1a8311..5de0630accfe 100644
--- a/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/echo_api/csharp/restsharp/net8/EchoApi/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -206,8 +206,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -216,10 +215,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Client/ClientUtils.cs
index d4d76fa0662c..d83b1e73aa81 100644
--- a/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/others/csharp-complex-files/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -215,8 +215,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -225,10 +224,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Client/ClientUtils.cs
index 2f93eb8fd38e..509d31240250 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore-nonPublicApi/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -221,8 +221,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -231,10 +230,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 5976bafe2823..32c391dc9a5f 100644
--- a/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/httpclient/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -221,8 +221,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -231,10 +230,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Client/ClientUtils.cs
index 2f93eb8fd38e..509d31240250 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -221,8 +221,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -231,10 +230,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 5976bafe2823..32c391dc9a5f 100644
--- a/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/httpclient/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -221,8 +221,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -231,10 +230,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 06699bfc386b..8e47a5169216 100644
--- a/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/httpclient/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -215,8 +215,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -225,10 +224,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
index 2f93eb8fd38e..509d31240250 100644
--- a/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -221,8 +221,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -231,10 +230,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 5976bafe2823..32c391dc9a5f 100644
--- a/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -221,8 +221,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -231,10 +230,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools.Test/Client/AcceptHeaderTests.cs b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools.Test/Client/AcceptHeaderTests.cs
new file mode 100644
index 000000000000..e180c7ca246b
--- /dev/null
+++ b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools.Test/Client/AcceptHeaderTests.cs
@@ -0,0 +1,46 @@
+using System.Net;
+using System.Net.Sockets;
+using System.Text;
+using System.Threading.Tasks;
+using Org.OpenAPITools.Api;
+using Xunit;
+
+namespace Org.OpenAPITools.Test.Client
+{
+    public sealed class AcceptHeaderTests
+    {
+        [Fact]
+        public void MixedResponseTypes_SendsAllAcceptTypesJsonFirst()
+        {
+            var port = FreePort();
+            using (var server = new HttpListener())
+            {
+                server.Prefixes.Add("http://127.0.0.1:" + port + "/");
+                server.Start();
+                var accept = Task.Run(() =>
+                {
+                    var ctx = server.GetContext();
+                    var sent = ctx.Request.Headers["Accept"];
+                    var body = Encoding.UTF8.GetBytes("{\"name\":\"doggie\",\"photoUrls\":[]}");
+                    ctx.Response.ContentType = "application/json";
+                    ctx.Response.OutputStream.Write(body, 0, body.Length);
+                    ctx.Response.Close();
+                    return sent;
+                });
+
+                new PetApi("http://127.0.0.1:" + port).GetPetById(1);
+
+                Assert.Equal("application/json,application/xml", accept.Result);
+            }
+        }
+
+        private static int FreePort()
+        {
+            var listener = new TcpListener(IPAddress.Loopback, 0);
+            listener.Start();
+            var port = ((IPEndPoint)listener.LocalEndpoint).Port;
+            listener.Stop();
+            return port;
+        }
+    }
+}
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Client/ClientUtils.cs
index 66e372d5c6d9..472b6c1ff87b 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/MultipleFrameworks/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -215,8 +215,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -225,10 +224,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 06699bfc386b..8e47a5169216 100644
--- a/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -215,8 +215,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -225,10 +224,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 06699bfc386b..8e47a5169216 100644
--- a/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -215,8 +215,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -225,10 +224,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
index 5976bafe2823..32c391dc9a5f 100644
--- a/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -221,8 +221,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -231,10 +230,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
index 7fa3d4709d28..8ad60804ffe9 100644
--- a/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/ParameterMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -205,8 +205,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -215,10 +214,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 5976bafe2823..32c391dc9a5f 100644
--- a/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -221,8 +221,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -231,10 +230,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index 27c78cc269c8..a642a2750b42 100644
--- a/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -205,8 +205,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -215,10 +214,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Client/ClientUtils.cs
index 02232ccae29f..238486a59320 100644
--- a/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net8/useVirtualForHooks/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -205,8 +205,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -215,10 +214,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
index 5976bafe2823..32c391dc9a5f 100644
--- a/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net9/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -221,8 +221,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -231,10 +230,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Client/ClientUtils.cs
index 06699bfc386b..8e47a5169216 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/ConditionalSerialization/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -215,8 +215,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -225,10 +224,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 06699bfc386b..8e47a5169216 100644
--- a/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -215,8 +215,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -225,10 +224,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/unityWebRequest/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/unityWebRequest/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index e4b650c9de82..a806c32691bf 100644
--- a/samples/client/petstore/csharp/unityWebRequest/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/unityWebRequest/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -205,8 +205,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -215,10 +214,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/unityWebRequest/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/unityWebRequest/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index e4b650c9de82..a806c32691bf 100644
--- a/samples/client/petstore/csharp/unityWebRequest/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/unityWebRequest/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -205,8 +205,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -215,10 +214,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>
diff --git a/samples/client/petstore/csharp/unityWebRequest/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/unityWebRequest/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 5d6275437696..fdb55b0718e3 100644
--- a/samples/client/petstore/csharp/unityWebRequest/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/unityWebRequest/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -199,8 +199,7 @@ public static string SelectHeaderContentType(string[] contentTypes)
 
         /// <summary>
         /// Select the Accept header's value from the given accepts array:
-        /// if JSON exists in the given array, use it;
-        /// otherwise use all of them (joining into a string)
+        /// all of them, JSON types first (joining into a string)
         /// </summary>
         /// <param name="accepts">The accepts array to select from.</param>
         /// <returns>The Accept header to use.</returns>
@@ -209,10 +208,7 @@ public static string SelectHeaderAccept(string[] accepts)
             if (accepts.Length == 0)
                 return null;
 
-            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
-                return "application/json";
-
-            return string.Join(",", accepts);
+            return string.Join(",", accepts.OrderBy(accept => IsJsonMime(accept) ? 0 : 1));
         }
 
         /// <summary>