Implementing Clean Architecture with .NET 5

Clean Architecture (Robert C. Martin) separates concerns into concentric rings, with the Domain at the center. Dependencies point inward. We implement this in .NET 5.

The Layers

flowchart TB
    subgraph Core ["Core (No Dependencies)"]
        Domain[Domain Entities]
        App[Application Use Cases]
    end
    
    subgraph Outer ["Infrastructure"]
        Infra[EF Core / SQL]
        API[Web API Controllers]
    end
    
    App --> Domain
    Infra --> App
    API --> App
    
    style Core fill:#FFF3E0,stroke:#E65100

The Dependency Rule

The Application layer defines interfaces (e.g., `IOrderRepository`), but the Infrastructure layer implements them. This “Inversion of Control” keeps the core independent of the database.

// Core/Interfaces/IOrderRepo.cs
public interface IOrderRepository
{
    Task SaveAsync(Order order);
}

// Infrastructure/Persistence/OrderRepo.cs
public class OrderRepository : IOrderRepository
{
    private readonly DbContext _context;
    public async Task SaveAsync(Order order) => await _context.AddAsync(order);
}

Key Takeaways

• Domain entities should have no external dependencies (no attribute tags if possible).
• Use CQRS (MediatR) in the Application layer to handle use cases.
• Infrastructure maps Domain entities to Database tables.