A Guide for Building a .NET Project with Clean Architecture

Create a new project with Clean Architecture in .NET

Creating a project with Clean Architecture in .NET involves organizing your codebase into distinct layers that prioritize separation of concerns, maintainability, and testability.

In this article we will take a closer look at the foundational thoughts and factors influencing our project creation.

Clean Architecture emphasizes the separation of concerns and dependency inversion to create a highly modular and testable codebase. The architecture is centered around layers that prioritize the business logic, keeping it isolated from external concerns like frameworks, databases, or UI.

Let’s dive into key principles of Clean Architecture.

Define Layers

• Presentation Layer (UI)
  • Contains the user interface components (e.g., MVC, API Controllers, Blazor components).
  • Communicates with the Application layer.
• Application Layer
  • Orchestrates the application's use cases or business logic.
  • Contains application services and interfaces.
  • Interacts with the Infrastructure layer and domain entities.
• Domain Layer
  • Represents the core business logic, entities, and domain-specific rules.
  • Contains domain entities, value objects, and domain services.
• Infrastructure Layer
  • Deals with external concerns like databases, file systems, APIs, etc.
  • Implements data access (repositories), external services, and other infrastructure-specific details.

Dependency Injection (DI)

• Utilize .NET's built-in DI container to manage dependencies between layers.
• Register dependencies and resolve them throughout the application.

Use Interfaces and Contracts

• Define interfaces and contracts to decouple components and layers. For instance, define interfaces for repositories, services, etc.
• Implement these interfaces in concrete classes within respective layers.

Separation of Concerns

• Ensure each layer has a specific responsibility and doesn't encroach on others.
• Maintain clear boundaries between layers.

Implement Patterns

• Repository Pattern
  • Encapsulate data access logic within repositories.
  • Interface-based approach for data retrieval and persistence.
• Use Case/Service Classes
  • Implement application-specific logic in use case or service classes within the Application layer.
• Dependency Inversion Principle (DIP)
  • Rely on abstractions/interfaces rather than concrete implementations to reduce coupling.

Unit Testing

• Write unit tests for each layer to ensure individual components work as expected.
• Mock dependencies for isolated testing.

Follow SOLID Principles

• Apply SOLID principles (Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion) throughout your architecture to ensure maintainability, flexibility, and extensibility.

Use Clean Code Practices

• Keep code clean, readable, and maintainable.
• Use meaningful names for classes, methods, and variables.
• Apply design patterns where appropriate to solve common architectural problems.

Continuous Refinement

• Regularly review and refine your architecture based on evolving requirements and feedback.

Documentation and Comments

• Provide meaningful comments and documentation where necessary to aid understanding for other developers and future maintenance.

Project Structure
 

MyProjectSolution/
│
├── MyProject.Application/       	(Application Layer)
│   ├── Services/                	(Application-specific services)
│   ├── UseCases/                	(Use case classes)
│   ├── Interfaces/              	(Interfaces defining application services)
│   └── MyProject.Application.csproj
│
├── MyProject.Domain/            	(Domain Layer)
│   ├── Entities/                	(Domain entities)
│   ├── ValueObjects/            	(Value objects)
│   ├── Interfaces/              	(Interfaces defining domain services)
│   └── MyProject.Domain.csproj
│
├── MyProject.Infrastructure/    	(Infrastructure Layer)
│   ├── Data/                    	(Data access, repositories)
│   ├── ExternalServices/        	(Integration with external services)
│   └── MyProject.Infrastructure.csproj
│
├── MyProject.Presentation/      	(Presentation Layer)
│   ├── Controllers/             	(API or MVC controllers)
│   ├── Models/                  	(ViewModels, DTOs)
│   └── MyProject.Presentation.csproj
│
├── MyProject.Tests/             	(Unit tests for each layer)
│   ├── ApplicationTests/
│   ├── DomainTests/
│   ├── InfrastructureTests/
│   └── MyProject.Tests.csproj
│
├── MyProject.sln                 	(Solution file)
└── README.md                     	(Documentation)

Benefits of using Clean Architecture

Clean Architecture offers numerous benefits that contribute to the overall quality, maintainability, and scalability of software systems. Here are some key advantages:

• Modifiability and Maintainability
  • Easier Updates: Clean Architecture promotes loose coupling, making it simpler to modify or replace components without affecting the entire system.
  • Isolated Changes: Modifications in one layer (such as UI or database) don’t necessitate changes in the core business logic, enhancing maintainability.
• Testability
  • Isolated Testing: The architecture’s layered structure allows for independent unit testing of components, aiding in comprehensive test coverage.
  • Mocking Dependencies: Interfaces and dependency injection enable the creation of mock objects, facilitating easier testing.
• Scalability
  • Clear Separation: Well-defined layers allow for scaling specific parts of the system without impacting others, enabling efficient scaling strategies.
  • Efficient Performance Improvements: Optimizations can be made at specific layers without affecting the entire system, ensuring performance enhancements are targeted.
• Reduced Technical Debt
  • Maintains Clean Code: By enforcing separation of concerns and clear boundaries, Clean Architecture reduces code entanglement and the accumulation of technical debt over time.
  • Easier Refactoring: It encourages continuous refactoring and cleaner code practices, minimizing the accumulation of legacy code.
• Enhanced Collaboration
  • Clear Structure: The architecture provides a clear structure and naming conventions, aiding communication and collaboration among team members.
  • Standardized Patterns: Consistent design patterns and principles foster a common understanding among developers, leading to more efficient collaboration.

Clean Architecture Sample Projects

Following are some example projects and open-source templates that use the Clean Architecture.

• Clean Architecture Solution Template for ASP.NET Core
• Clean Architecture Solution Template: A starting point for Clean Architecture with ASP.NET Core
• Clean Architecture Template for Blazor WebAssembly Built with MudBlazor Components.

Conclusion

Implementing Clean Architecture principles in a .NET project involves separating concerns, defining clear boundaries between layers, and ensuring testability and maintainability. This approach facilitates easier modifications, enhances code readability, and simplifies testing.