Implementing Clean Architecture in .NET

A practical guide to implementing Clean Architecture principles in .NET applications with real-world examples

Architecture .NET DDD Clean Code

Introduction

Clean Architecture, popularized by Robert C. Martin (Uncle Bob), provides a way to organize code that makes it:

  • Independent of frameworks - The architecture doesn’t depend on external libraries
  • Testable - Business rules can be tested without UI, database, or external elements
  • Independent of UI - The UI can change without changing the rest of the system
  • Independent of Database - Business rules are not bound to the database

The Layers

Domain Layer

The innermost layer contains:

  • Entities
  • Value Objects
  • Domain Events
  • Interfaces (repository contracts)
public class Order : Entity
{
    public OrderId Id { get; private set; }
    public CustomerId CustomerId { get; private set; }
    public OrderStatus Status { get; private set; }

    public void Confirm()
    {
        if (Status != OrderStatus.Pending)
            throw new InvalidOperationException();

        Status = OrderStatus.Confirmed;
        AddDomainEvent(new OrderConfirmedEvent(this));
    }
}

Application Layer

Contains use cases and application-specific business rules:

public class ConfirmOrderHandler : IRequestHandler<ConfirmOrderCommand>
{
    private readonly IOrderRepository _orderRepository;

    public async Task Handle(ConfirmOrderCommand request)
    {
        var order = await _orderRepository.GetByIdAsync(request.OrderId);
        order.Confirm();
        await _orderRepository.SaveAsync(order);
    }
}

Key Benefits

  1. Maintainability - Changes in one layer don’t affect others
  2. Testability - Easy to write unit tests for business logic
  3. Flexibility - Easy to swap implementations

Conclusion

Clean Architecture requires more initial setup, but the long-term benefits in maintainability and testability make it worthwhile for complex applications.

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