Clean Architecture in .NET: A Practical Guide

The Core Idea

Dependencies point inward. The domain layer knows nothing about EF Core, ASP.NET, or SQL Server. Outer layers depend on inner layers — never the reverse.

Project Structure

MyApp.Domain        ← Entities, value objects, domain events
MyApp.Application   ← Use cases, interfaces, DTOs
MyApp.Infrastructure← EF Core, external APIs, file storage
MyApp.Web           ← ASP.NET Core, controllers, Razor Pages

Repository Pattern

// In Application layer — no EF Core reference
public interface IPostRepository
{
    Task<BlogPost?> GetBySlugAsync(string slug);
    Task<IReadOnlyList<BlogPost>> GetPublishedAsync(int page, int size);
}

// In Infrastructure layer — EF Core implementation
public class PostRepository(BlogDbContext db) : IPostRepository
{
    public Task<BlogPost?> GetBySlugAsync(string slug) =>
        db.BlogPosts.AsNoTracking().FirstOrDefaultAsync(p => p.Slug == slug);
}

Conclusion

Clean Architecture pays dividends on large teams and long-lived systems. Apply it where complexity justifies the overhead.