clean-architecture

Clean Architecture for .NET

Reference for architectural decisions. Used by dnp-architect and dnp-planner.

Layer Definitions

Domain (innermost)

• Contains: Entities, value objects, domain events, domain exceptions, enums
• References: Nothing (zero project references)
• Packages allowed: MediatR.Contracts (interfaces only), FluentResults
• Packages forbidden: EF Core, ASP.NET Core, any infrastructure

Application

• Contains: Service interfaces, DTOs, validators, MediatR handlers, mapping profiles
• References: Domain only
• Packages allowed: MediatR, FluentValidation, AutoMapper
• Packages forbidden: EF Core, database drivers, HTTP clients

Infrastructure

• Contains: DbContext, repositories, external service clients, email senders
• References: Domain, Application
• Packages allowed: EF Core, database drivers, HTTP clients, file system
• Implements: Interfaces defined in Application

API/Web (outermost)

• Contains: Controllers/endpoints, middleware, Program.cs, DI composition root
• References: Application, Infrastructure
• Packages allowed: Swashbuckle, authentication, rate limiting
• Responsibility: Wire everything together, no business logic

Tests

• References: Any (unrestricted)
• Packages: Test framework, mocking library, assertions, WebApplicationFactory

DI Registration Pattern

// In Infrastructure project:
public static class InfrastructureServiceExtensions
{
    public static IServiceCollection AddInfrastructureServices(
        this IServiceCollection services, IConfiguration config)
    {
        services.AddDbContext<ApplicationDbContext>(options =>
            options.UseNpgsql(config.GetConnectionString("DefaultConnection")));

        services.AddScoped<IUserRepository, UserRepository>();
        return services;
    }
}

// In Application project:
public static class ApplicationServiceExtensions
{
    public static IServiceCollection AddApplicationServices(this IServiceCollection services)
    {
        services.AddScoped<IUserService, UserService>();
        services.AddMediatR(cfg => cfg.RegisterServicesFromAssembly(typeof(ApplicationServiceExtensions).Assembly));
        return services;
    }
}

// In Program.cs (API project):
builder.Services.AddApplicationServices();
builder.Services.AddInfrastructureServices(builder.Configuration);

Validation Rules

Rule	Check
Domain independence	Domain .csproj has 0 <ProjectReference> elements
Application → Domain only	Application .csproj references only Domain
No reverse dependencies	Domain never references Application/Infrastructure/API
Interface segregation	Application defines interfaces, Infrastructure implements
Composition root	Only API project wires DI container