🚀Clean Architecture in .NET

Introduction

Hello, fellow developers! 👋 Hope you’re doing well.

In the world of software architecture, structuring our code properly is crucial for maintainability, scalability, and testability. In our last discussion, we explored different architectural patterns, including Hexagonal Architecture, Layered Architecture, Onion Architecture, and Clean Architecture.

Today, we’re going to dive deep into Clean Architecture, what it is, why it matters, and how we can implement it in a real-world .NET application. 💡

The full source code is available on GitHub, so feel free to download it and follow along! 🛠️

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What is Clean Architecture? 🤔

Clean Architecture, introduced by Uncle Bob (Robert C. Martin), is a domain-centric approach that helps us build software that is:

✅ Flexible – Easy to swap technologies (databases, frameworks, UI).

✅ Maintainable – Well-structured code with minimal dependencies.

✅ Testable – Business logic remains independent of external concerns.

Layer Breakdown 🏗️

Clean Architecture is structured into four key layers:

1️⃣ Domain Layer (Core Business Logic) – Contains entities, value objects, and domain services.

2️⃣ Application Layer (Use Cases & CQRS) – Defines business rules, CQRS commands/queries, and interfaces.

3️⃣ Infrastructure Layer (Implementations & DB Access) – Implements interfaces from the Application Layer.

4️⃣ Presentation Layer (API/UI Controllers) – Exposes the functionality via endpoints or UI.

At its core, Clean Architecture follows the Dependency Rule:

Inner layers should not depend on outer layers.

This means that business logic is independent of frameworks, databases, and UI technologies. 🚀

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Implementing Clean Architecture in .NET 🏗️

Let’s break down how we’ve structured a .NET application using Clean Architecture principles.

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1️⃣ Domain Layer – The Heart of Clean Architecture

The Domain Layer is the most important part of Clean Architecture. It contains:

✅ Entities (Book, Person) – Define core data structures.

✅ Value Objects (Genre, Address) – Immutable objects with validation.

✅ BaseEntity & BaseAuditableEntity – Common properties like Id, CreatedDate, UpdatedDate.

✅ Domain Exceptions (UnsupportedGenreException) – Custom exceptions for domain-level errors.

✅ Domain Events – Handling important business events.

A key decision here:

📌 Using DateTimeOffset instead of DateTime ensures proper time zone handling across different regions.

👉 The Domain Layer has no dependencies on external frameworks or databases, keeping it pure and reusable.

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2️⃣ Application Layer – Business Logic & CQRS

The Application Layer is where we define use cases and business rules. It consists of:

✅ CQRS (Command Query Responsibility Segregation) – Separating read and write operations.

✅ Interfaces (e.g., IEmailService) – Abstractions for external dependencies.

✅ Command Handlers (CreateBookCommandHandler, DeleteBookCommandHandler).

✅ Validation Rules – Using FluentValidation to enforce constraints.

✅ Unit of Work Pattern – Ensuring atomic transactions.

📌 Key concept:

• Commands modify data (CreateBookCommand, UpdateBookCommand).
• Queries retrieve data (GetBookByIdQuery).
• The Application Layer only contains interfaces, keeping it decoupled from the infrastructure.

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3️⃣ Infrastructure Layer – Implementation Details

The Infrastructure Layer provides concrete implementations of the interfaces defined in the Application Layer. It includes:

✅ Entity Framework Core (EF Core) Configuration – Setting up database persistence.

✅ ApplicationDbContext – The actual database context.

✅ Unit of Work Implementation – Managing transactions efficiently.

✅ Email Service Implementation – Sending emails using external services.

✅ Global Exception Handling – Standardizing error responses.

📌 Infrastructure should depend on Application, not the other way around. This keeps the core logic flexible while allowing technology choices to change without affecting the domain.

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4️⃣ Presentation Layer – Exposing APIs & Dependency Injection

The Presentation Layer (CleanArchitecture.API) is the entry point of the application, responsible for:

✅ API Controllers – Handling requests and responses.

✅ Swagger Documentation – Interactive API documentation.

✅ Dependency Injection (DI) Setup – Registering services.

✅ Global Exception Handling – Formatting errors consistently.

📌 In Program.cs, we wire everything together:

builder.Services.AddApplicationServices();  
builder.Services.AddInfrastructureServices();  
builder.Services.AddPresentationServices();  

This ensures all dependencies are properly injected across the application.

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Key Benefits of Clean Architecture 🏆

✅ Separation of Concerns – Code is modular and easier to maintain.

✅ Scalability – Easily swap out technologies without major refactoring.

✅ Testability – Business logic remains independent and can be tested in isolation.

✅ Flexibility – The application can evolve over time with minimal disruption.

By following this structure, we ensure our .NET applications are robust, maintainable, and scalable. 🚀

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Wrapping Up & Next Steps

That’s a complete walkthrough of Clean Architecture in .NET! 🎉

💡 What’s Next?

• 🔥 Download the source code from my GitHub repo and try it yourself!
• 👍 If you found this helpful, give it a star on GitHub!
• 📢 Have questions? Drop a comment below!
• 🔔 Subscribe for more .NET & Software Architecture content!

Thanks for reading, and happy coding! 🎯