Clean Architecture with .NET 8: A Practical Guide

Clean Architecture has become a cornerstone principle in modern software development, yet many teams struggle with its practical implementation. Let's explore how to apply these principles effectively in .NET 8 applications.

Understanding the Core Principles

Clean Architecture, introduced by Robert C. Martin, emphasizes separation of concerns and dependency inversion. The architecture is organized in concentric circles, where inner circles represent business logic and outer circles represent implementation details.

The key benefit is that your business logic remains independent of frameworks, databases, and UI implementations. This independence makes your codebase more testable, maintainable, and adaptable to change.

Layer Structure in .NET 8

In a typical .NET 8 solution following Clean Architecture, you'll have these projects:

• Domain — Contains entities, value objects, and domain events
• Application — Houses business logic, use cases, and interfaces
• Infrastructure — Implements data access, external services, and frameworks
• Web/API — Presentation layer with controllers and views

Implementing the Domain Layer

The Domain layer is the heart of your application. It contains your business entities with rich behavior, not anemic data models. Here's what makes a good domain entity:

Entities should encapsulate business rules and maintain their own invariants. Use private setters and expose behavior through methods. Validate state changes within the entity itself, ensuring that invalid states are impossible to represent.

Application Layer Best Practices

The Application layer orchestrates the flow of data and coordinates domain objects to perform use cases. This is where CQRS (Command Query Responsibility Segregation) shines in .NET applications.

Using MediatR for implementing CQRS patterns provides a clean way to handle commands and queries. Each use case becomes a discrete handler, making your code easier to test and maintain. The Application layer should define interfaces for infrastructure concerns, following the Dependency Inversion Principle.

Infrastructure Concerns

The Infrastructure layer is where you implement the interfaces defined in the Application layer. This includes database access with Entity Framework Core, external API integrations, file systems, and caching mechanisms.

Keep your infrastructure implementations focused and testable. Use the Repository pattern judiciously — don't create a repository for every entity. Instead, consider using aggregates and designing repositories around them.

Testing Your Architecture

One of Clean Architecture's greatest strengths is testability. Your domain logic can be tested in complete isolation. Application layer handlers can be tested with mocked infrastructure dependencies.

Write unit tests for your domain entities and value objects. Use integration tests for application handlers with real database implementations. Reserve end-to-end tests for critical user journeys through your API.

Conclusion

Clean Architecture provides a solid foundation for building maintainable .NET applications, but it's not a silver bullet. Apply these principles pragmatically, adapting them to your team's needs and project constraints.

Start with a simpler structure and evolve toward Clean Architecture as your application grows. The goal is sustainable development velocity, not architectural purity for its own sake.