Clean Architecture with ASP.NET Core 9

Summary

This video delves into Clean Architecture, covering essential concepts like domain events, CQRS, and structuring applications with core, infrastructure, and web layers. The speaker demonstrates a sample project that illustrates how domain events can decouple business logic from side effects, such as sending emails upon task completion. With a focus on maintainability and separation of concerns, the video emphasizes the importance of using patterns like behaviors and specifications. It also introduces a Clean Architecture template for .NET, showcasing how easily developers can set up a scalable, organized application structure.

Takeaways

• 😀 Clean Architecture emphasizes separation of concerns, organizing projects into core, infrastructure, and web layers for maintainability and scalability.
• 😀 The Core layer contains the business logic, domain entities, domain events, and specifications, all without infrastructure dependencies to keep the system testable.
• 😀 The Infrastructure layer handles real-world services like data access, API clients, and external systems (e.g., email or SMS), keeping them separate from core logic.
• 😀 The Web layer is responsible for web-related services, such as API endpoints and Razor Pages, and wires up interfaces to their implementations.
• 😀 Domain events are a key pattern in Clean Architecture, used to decouple operations (like sending emails) from the core business logic.
• 😀 Use Case layer implements CQRS (Command Query Responsibility Segregation) to handle commands and queries separately for improved efficiency.
• 😀 Behaviors, implemented as middleware, wrap commands and queries to handle cross-cutting concerns like logging, validation, and timing.
• 😀 The application avoids tight coupling by using domain events and handlers, ensuring side effects (like email sending) are handled independently from business logic.
• 😀 The demo application uses domain events to trigger email notifications when tasks are completed, demonstrating the decoupling of business logic and side effects.
• 😀 The Clean Architecture template is available through the `dotnet new clean-architecture` command, providing a structured starting point for building applications with Clean Architecture.
• 😀 The sample code and architecture demonstrated in the presentation are compatible with .NET 9, offering improved performance and easier upgrades from earlier versions.

Q & A

What is the main goal of clean architecture in the context of software development?

The main goal of clean architecture is to organize software into distinct layers that separate concerns, making the code more maintainable, testable, and flexible. It promotes the idea of decoupling business logic from infrastructure and presentation layers.

Why is it important to use specific exceptions like 'Order Required Exception' instead of general ones like 'NullReferenceException'?

Using specific exceptions like 'Order Required Exception' provides clearer context when debugging. It helps developers understand exactly where the issue is in the code, making it easier to address the problem compared to a general 'NullReferenceException', which does not provide enough information.

How do domain events improve the separation of concerns in an application?

Domain events allow side effects (like sending emails or notifications) to be handled separately from core business logic. This keeps the business logic focused on its core responsibilities while external actions are handled by event handlers, ensuring clear separation and modularity.

What role do specifications play in clean architecture?

Specifications encapsulate complex query logic, preventing it from being scattered throughout the application. This pattern allows queries to be defined in a reusable and clean manner, centralizing query logic and improving maintainability.

Can you explain the concept of Command Query Responsibility Segregation (CQRS)?

CQRS is an architectural pattern where commands (which modify data) and queries (which retrieve data) are handled separately. This allows each to be optimized independently, leading to better performance and clearer organization of business operations.

What is the purpose of the 'Behaviors' pattern mentioned in the presentation?

Behaviors act as middleware for commands and queries, allowing cross-cutting concerns like logging, validation, or timing to be applied without cluttering the core logic. They can be chained together to apply multiple behaviors in a flexible and reusable way.

How does the infrastructure layer fit into clean architecture?

The infrastructure layer contains components that interact with external systems, such as databases, APIs, file systems, and third-party services. It abstracts these interactions from the core business logic, allowing for easier unit testing and decoupling from implementation details.

In the demo, how is an email notification triggered when a to-do item is marked as complete?

When a to-do item is marked as complete, a domain event is triggered. This event is handled by an event handler, which then sends an email to notify the user. The email sending logic is decoupled from the business logic of completing the task, thanks to the use of domain events.

What does the clean architecture template provide to developers?

The clean architecture template provides a pre-configured solution structure, including core, infrastructure, and web layers, to help developers organize their applications following clean architecture principles. It serves as a starting point for building scalable and maintainable applications.

Why should developers consider upgrading to .NET 9 as mentioned in the video?

Upgrading to .NET 9 provides the latest features, improvements, and optimizations, making development smoother and more efficient. The speaker highlights that upgrading from .NET 8 to .NET 9 was easy, and it supports the latest version of the clean architecture template.