Implementing Clean Architecture in .NET

Clean Architecture is a software design philosophy that separates concerns into distinct layers, making your .NET applications more maintainable, testable, and scalable.

Core Principles

Clean Architecture follows these fundamental principles:

Layer Structure

Domain Layer (Core)

• Entities: Business objects with identity
• Value Objects: Immutable objects without identity
• Domain Events: Events that occur in the domain
• Exceptions: Domain-specific exceptions

public class Order
{
    public Guid Id { get; private set; }
    public OrderStatus Status { get; private set; }
    public List<OrderItem> Items { get; private set; }
    
    public void AddItem(OrderItem item)
    {
        if (Status != OrderStatus.Draft)
            throw new InvalidOperationException("Cannot modify a confirmed order");
            
        Items.Add(item);
    }
}

Application Layer

• Use Cases: Application-specific business rules
• Interfaces: Abstractions for external dependencies
• DTOs: Data transfer objects
• Validators: Input validation logic

public class CreateOrderCommand : IRequest<OrderDto>
{
    public Guid CustomerId { get; set; }
    public List<OrderItemDto> Items { get; set; }
}</p><p>public class CreateOrderHandler : IRequestHandler<CreateOrderCommand, OrderDto>
{
    private readonly IOrderRepository <em>repository;
    
    public async Task<OrderDto> Handle(CreateOrderCommand request, CancellationToken ct)
    {
        var order = Order.Create(request.CustomerId);
        
        foreach (var item in request.Items)
            order.AddItem(new OrderItem(item.ProductId, item.Quantity));
            
        await </em>repository.AddAsync(order);
        
        return order.ToDto();
    }
}

Infrastructure Layer

• Data Access: Entity Framework, Dapper
• External Services: Email, SMS, Payment gateways
• File System: File storage implementation

Presentation Layer

• API Controllers: REST endpoints
• SignalR Hubs: Real-time communication
• Background Jobs: Hangfire, Quartz

CQRS Pattern Integration

Clean Architecture works beautifully with CQRS (Command Query Responsibility Segregation):

Commands (Write operations):

public class UpdateOrderStatusCommand : IRequest
{
    public Guid OrderId { get; set; }
    public OrderStatus NewStatus { get; set; }
}

Queries (Read operations):

public class GetOrderByIdQuery : IRequest<OrderDto>
{
    public Guid OrderId { get; set; }
}

Benefits in .NET

Common Pitfalls

❌ Anemic Domain Model: Don't just make DTOs in the domain layer ❌ Circular Dependencies: Use dependency inversion ❌ Leaky Abstractions: Keep domain logic in domain layer ❌ Over-engineering: Start simple, add complexity when needed

Conclusion

Clean Architecture in .NET provides a solid foundation for building maintainable enterprise applications. By separating concerns and following the dependency rule, you create systems that are easier to test, modify, and scale.

The initial setup might seem like overhead, but the long-term benefits in maintenance, testing, and team collaboration far outweigh the upfront cost.