Onion Architecture: add the Banking sample on .NET 10

csharp-architectural-patterns/OnionArchitecture/.gitignore

@@ -0,0 +1,4 @@
+# SQLite database the API creates on first run (EnsureCreated)
+*.db
+*.db-shm
+*.db-wal

csharp-architectural-patterns/OnionArchitecture/Banking.Api/AccountEndpoints.cs

@@ -0,0 +1,35 @@
+using System.ComponentModel.DataAnnotations;
+using Banking.Services;
+
+namespace Banking.Api;
+
+public sealed record WithdrawRequest([property: Range(typeof(decimal), "1", "1000")] decimal Amount);
+
+public static class AccountEndpoints
+{
+    public static void MapAccountEndpoints(this IEndpointRouteBuilder app)
+    {
+        var accounts = app.MapGroup("/api/accounts");
+
+        accounts.MapGet("/{accountId:int}", async (
+            int accountId,
+            IAccountService service,
+            CancellationToken cancellationToken) =>
+        {
+            var result = await service.GetByIdAsync(accountId, cancellationToken);
+
+            return result.IsSuccess ? Results.Ok(result.Value) : result.ToProblem();
+        });
+
+        accounts.MapPost("/{accountId:int}/withdrawals", async (
+            int accountId,
+            WithdrawRequest request,
+            IAccountService service,
+            CancellationToken cancellationToken) =>
+        {
+            var result = await service.WithdrawAsync(accountId, request.Amount, cancellationToken);
+
+            return result.IsSuccess ? Results.Ok(result.Value) : result.ToProblem();
+        });
+    }
+}

csharp-architectural-patterns/OnionArchitecture/Banking.Api/Banking.Api.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <ItemGroup>
+    <ProjectReference Include="..\Banking.Services\Banking.Services.csproj" />
+    <ProjectReference Include="..\Banking.Infrastructure\Banking.Infrastructure.csproj" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+</Project>

csharp-architectural-patterns/OnionArchitecture/Banking.Api/Banking.Api.http

@@ -0,0 +1,26 @@
+GET http://localhost:5000/api/accounts/1
+
+###
+
+POST http://localhost:5000/api/accounts/1/withdrawals
+Content-Type: application/json
+
+{ "amount": 30 }
+
+###
+
+POST http://localhost:5000/api/accounts/2/withdrawals
+Content-Type: application/json
+
+{ "amount": 50 }
+
+###
+
+POST http://localhost:5000/api/accounts/1/withdrawals
+Content-Type: application/json
+
+{ "amount": 0 }
+
+###
+
+GET http://localhost:5000/api/accounts/99

csharp-architectural-patterns/OnionArchitecture/Banking.Api/Program.cs

@@ -0,0 +1,25 @@
+using Banking.Api;
+using Banking.Infrastructure;
+using Banking.Services;
+
+var builder = WebApplication.CreateBuilder(args);
+
+builder.Services.AddServices();
+builder.Services.AddInfrastructure(builder.Configuration.GetConnectionString("Banking")!);
+
+builder.Services.AddProblemDetails();
+builder.Services.AddValidation();
+
+var app = builder.Build();
+
+app.UseExceptionHandler();
+
+using (var scope = app.Services.CreateScope())
+{
+    var dbContext = scope.ServiceProvider.GetRequiredService<BankingDbContext>();
+    dbContext.Database.EnsureCreated();
+}
+
+app.MapAccountEndpoints();
+
+app.Run();

csharp-architectural-patterns/OnionArchitecture/Banking.Api/Properties/launchSettings.json

@@ -0,0 +1,23 @@
+{
+  "$schema": "https://json.schemastore.org/launchsettings.json",
+  "profiles": {
+    "http": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": true,
+      "applicationUrl": "http://localhost:5000",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    },
+    "https": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": true,
+      "applicationUrl": "https://localhost:7254;http://localhost:5000",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    }
+  }
+}

csharp-architectural-patterns/OnionArchitecture/Banking.Api/ResultExtensions.cs

@@ -0,0 +1,21 @@
+using Banking.Domain;
+
+namespace Banking.Api;
+
+public static class ResultExtensions
+{
+    public static IResult ToProblem(this Result result)
+    {
+        var error = result.Error
+            ?? throw new InvalidOperationException("A successful result is not a problem.");
+
+        var statusCode = error.Type switch
+        {
+            ErrorType.NotFound => StatusCodes.Status404NotFound,
+            ErrorType.Conflict => StatusCodes.Status409Conflict,
+            _ => StatusCodes.Status500InternalServerError
+        };
+
+        return TypedResults.Problem(statusCode: statusCode, title: error.Code, detail: error.Description);
+    }
+}

csharp-architectural-patterns/OnionArchitecture/Banking.Api/appsettings.Development.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

csharp-architectural-patterns/OnionArchitecture/Banking.Api/appsettings.json

@@ -0,0 +1,12 @@
+{
+  "ConnectionStrings": {
+    "Banking": "Data Source=banking.db"
+  },
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}

csharp-architectural-patterns/OnionArchitecture/Banking.ArchitectureTests/Banking.ArchitectureTests.csproj

@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.10.1" />
+    <PackageReference Include="NetArchTest.Rules" Version="1.3.2" />
+    <PackageReference Include="xunit.v3.mtp-off" Version="4.0.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="4.0.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Banking.Api\Banking.Api.csproj" />
+  </ItemGroup>
+
+</Project>

csharp-architectural-patterns/OnionArchitecture/Banking.ArchitectureTests/LayerTests.cs

@@ -0,0 +1,45 @@
+using Banking.Api;
+using Banking.Domain;
+using Banking.Services;
+using NetArchTest.Rules;
+
+namespace Banking.ArchitectureTests;
+
+public class LayerTests
+{
+    [Fact]
+    public void Domain_DependsOnNoOtherLayer()
+    {
+        var result = Types.InAssembly(typeof(Account).Assembly)
+            .ShouldNot()
+            .HaveDependencyOnAny("Banking.Services", "Banking.Infrastructure", "Banking.Api")
+            .GetResult();
+
+        Assert.True(result.IsSuccessful, "Offending types: " + string.Join(", ", result.FailingTypeNames ?? []));
+    }
+
+    [Fact]
+    public void Services_DoNotDependOnTheOuterRing()
+    {
+        var result = Types.InAssembly(typeof(IAccountService).Assembly)
+            .ShouldNot()
+            .HaveDependencyOnAny("Banking.Infrastructure", "Banking.Api",
+                "Microsoft.EntityFrameworkCore", "Microsoft.AspNetCore")
+            .GetResult();
+
+        Assert.True(result.IsSuccessful, "Offending types: " + string.Join(", ", result.FailingTypeNames ?? []));
+    }
+
+    [Fact]
+    public void Endpoints_GoThroughTheServices()
+    {
+        var result = Types.InAssembly(typeof(AccountEndpoints).Assembly)
+            .That()
+            .ResideInNamespace("Banking.Api")
+            .ShouldNot()
+            .HaveDependencyOnAny("Banking.Infrastructure", "Banking.Domain.IAccountRepository")
+            .GetResult();
+
+        Assert.True(result.IsSuccessful, "Offending types: " + string.Join(", ", result.FailingTypeNames ?? []));
+    }
+}

csharp-architectural-patterns/OnionArchitecture/Banking.Domain/Account.cs

@@ -0,0 +1,34 @@
+namespace Banking.Domain;
+
+public sealed class Account
+{
+    private Account(string owner, decimal balance)
+    {
+        Owner = owner;
+        Balance = balance;
+    }
+
+    public int Id { get; private set; }
+    public string Owner { get; private set; }
+    public decimal Balance { get; private set; }
+
+    public static Account Open(string owner, decimal initialDeposit)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(owner);
+        ArgumentOutOfRangeException.ThrowIfNegative(initialDeposit);
+
+        return new Account(owner, initialDeposit);
+    }
+
+    public Result Withdraw(decimal amount)
+    {
+        ArgumentOutOfRangeException.ThrowIfNegativeOrZero(amount);
+
+        if (amount > Balance)
+            return AccountErrors.InsufficientFunds(Id);
+
+        Balance -= amount;
+
+        return Result.Success();
+    }
+}

csharp-architectural-patterns/OnionArchitecture/Banking.Domain/AccountErrors.cs

@@ -0,0 +1,10 @@
+namespace Banking.Domain;
+
+public static class AccountErrors
+{
+    public static Error NotFound(int accountId) =>
+        new("Account.NotFound", $"Account {accountId} was not found.", ErrorType.NotFound);
+
+    public static Error InsufficientFunds(int accountId) =>
+        new("Account.InsufficientFunds", $"Account {accountId} doesn't have enough money for this withdrawal.", ErrorType.Conflict);
+}

csharp-architectural-patterns/OnionArchitecture/Banking.Domain/Banking.Domain.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

csharp-architectural-patterns/OnionArchitecture/Banking.Domain/IAccountRepository.cs

@@ -0,0 +1,8 @@
+namespace Banking.Domain;
+
+public interface IAccountRepository
+{
+    Task<Account?> GetByIdAsync(int accountId, CancellationToken cancellationToken = default);
+
+    Task SaveChangesAsync(CancellationToken cancellationToken = default);
+}

csharp-architectural-patterns/OnionArchitecture/Banking.Domain/Result.cs

@@ -0,0 +1,39 @@
+namespace Banking.Domain;
+
+public enum ErrorType
+{
+    NotFound,
+    Conflict
+}
+
+public sealed record Error(string Code, string Description, ErrorType Type);
+
+public class Result
+{
+    protected Result(Error? error) => Error = error;
+
+    public Error? Error { get; }
+    public bool IsSuccess => Error is null;
+
+    public static Result Success() => new(null);
+
+    public static implicit operator Result(Error error) => new(error);
+}
+
+public sealed class Result<TValue> : Result
+{
+    private readonly TValue? _value;
+
+    private Result(TValue? value, Error? error)
+        : base(error) => _value = value;
+
+    public TValue Value => IsSuccess
+        ? _value!
+        : throw new InvalidOperationException("A failed result has no value.");
+
+    public static implicit operator Result<TValue>(TValue value) =>
+        new(value, null);
+
+    public static implicit operator Result<TValue>(Error error) =>
+        new(default, error);
+}

csharp-architectural-patterns/OnionArchitecture/Banking.Infrastructure/AccountRepository.cs

@@ -0,0 +1,13 @@
+using Banking.Domain;
+using Microsoft.EntityFrameworkCore;
+
+namespace Banking.Infrastructure;
+
+internal sealed class AccountRepository(BankingDbContext dbContext) : IAccountRepository
+{
+    public Task<Account?> GetByIdAsync(int accountId, CancellationToken cancellationToken = default) =>
+        dbContext.Accounts.FirstOrDefaultAsync(a => a.Id == accountId, cancellationToken);
+
+    public Task SaveChangesAsync(CancellationToken cancellationToken = default) =>
+        dbContext.SaveChangesAsync(cancellationToken);
+}

csharp-architectural-patterns/OnionArchitecture/Banking.Infrastructure/Banking.Infrastructure.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <ItemGroup>
+    <ProjectReference Include="..\Banking.Domain\Banking.Domain.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="10.0.12" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>