Architectural Patterns with .NET Core: An In-Depth Guide

In this article, we will explore various architectural patterns with .NET Core. These patterns are essential for building scalable, maintainable, and robust applications. We will delve into each pattern, explaining its use case, benefits, and providing detailed C# examples.

1. Event-Driven Architecture

Event-Driven Architecture is a pattern where the application components communicate through the production and consumption of events.

Why Use Event-Driven Architecture?

• Scalability: Components can scale independently.
• Decoupling: Reduces the dependency between components.
• Responsiveness: Improves system responsiveness by processing events asynchronously.

Setup

To implement Event-Driven Architecture in .NET Core, we can use libraries such as MediatR for in-process messaging or MassTransit for messaging with external brokers like RabbitMQ.

Example

Problem Statement

You have an e-commerce application where various services (Inventory, Shipping, Notification) need to respond to an OrderPlaced event.

C# Code Example

In this example:

• OrderService produces the OrderPlacedEvent.
• InventoryService consumes the OrderPlacedEvent to update the inventory.

2. Layered Architecture

Layered Architecture divides the application into layers such as Presentation, Business, Persistence, and Database.

Why Use Layered Architecture?

• Separation of Concerns: Each layer has a distinct responsibility.
• Maintainability: Changes in one layer do not affect others.
• Testability: Layers can be tested independently.

Setup

In .NET Core, you can create separate projects or folders for each layer.

Example

Problem Statement

You need to create a web application that handles user requests, processes business logic, and interacts with a database.

C# Code Example

In this example:

• UserController handles HTTP requests and responses.
• UserService contains business logic.
• UserRepository interacts with the database

3. Monolithic Architecture

Monolithic Architecture is a single, unified application where all components are interconnected and run as a single service.

Why Use Monolithic Architecture?

• Simplicity: Easier to develop, test, and deploy.
• Performance: Lower latency due to fewer network calls.
• Deployment: Single deployment unit simplifies deployment processes.

Setup

A typical monolithic application in .NET Core might be organized as a single project.

Example

Problem Statement

You need to build a blog application where all functionalities (Posts, Comments, Users) are tightly coupled and deployed together.

C# Code Example

In this example, BlogService handles all operations related to posts and comments within a single application context.

4. Microservice Architecture

Microservice Architecture decomposes the application into loosely coupled, independently deployable services.

Why Use Microservice Architecture?

• Scalability: Each service can scale independently.
• Resilience: Failure in one service does not affect others.
• Flexibility: Services can be developed and deployed independently.

Setup

In .NET Core, each microservice can be a separate ASP.NET Core project, often communicating via REST APIs or messaging.

Example

Problem Statement

You have an online store with services for catalog, shopping cart, and ordering, each needing to scale independently.

C# Code Example

In this example:

• CatalogController and ShoppingCartController are separate services, each handling different aspects of the online store.

5. Pipe and Filter Architecture

Pipe and Filter Architecture involves processing data through a sequence of filters, each performing a specific transformation.

Why Use Pipe and Filter Architecture?

• Reusability: Filters can be reused in different pipelines.
• Modularity: Easy to add, remove, or modify filters.
• Parallelism: Filters can process data concurrently.

Setup

In .NET Core, you can implement filters as separate classes and chain them together in a pipeline.

Example

Problem Statement

You need to process a stream of data through a series of transformations (e.g., validation, enrichment, formatting).

C# Code Example

In this example:

• Pipeline executes a series of filters (ValidationFilter, EnrichmentFilter) on the input data.

6. Peer-to-Peer Architecture

Peer-to-Peer Architecture consists of a network of peers, where each peer can act as both a client and a server.

Why Use Peer-to-Peer Architecture?

• Decentralization: No single point of failure.
• Scalability: Each peer can contribute resources.
• Robustness: Network can self-heal and reconfigure.

Setup

In .NET Core, you can use libraries like LiteNetLib or build custom TCP/UDP-based communication.

Example

Problem Statement

You need to build a file-sharing application where users can share files directly with each other.

C# Code Example

In this example:

• Peer class handles file sharing by listening for incoming connections and managing files.

7. Model-View-Controller (MVC) Architecture

MVC Architecture separates an application into three main components: Model, View, and Controller.

Why Use MVC Architecture?

• Separation of Concerns: Clear separation between data, UI, and logic.
• Testability: Each component can be tested independently.
• Maintainability: Easier to manage and scale.

Setup

In .NET Core, you can use the built-in MVC framework.

Example

Problem Statement

You need to create a web application that separates data handling, UI rendering, and user input processing.

C# Code Example

In this example:

• Product model represents the data.
• ProductController handles user input and processes business logic.
• Index.cshtml view renders the UI.

8. Primary-Replica Architecture

Primary-Replica Architecture involves a primary server handling write operations and multiple replica servers handling read operations.

Why Use Primary-Replica Architecture?

• Scalability: Read operations can be scaled horizontally.
• Availability: Increased availability for read-heavy applications.
• Fault Tolerance: Replica servers can take over if the primary server fails.

Setup

In .NET Core, you can configure primary and replica databases using connection strings and a database context.

Example

Problem Statement

You need to build a high-availability application where read and write operations are distributed across different servers.

C# Code Example

In this example:

• AppDbContext is configured to use a primary database for write operations.
• ProductRepository handles data access, using the primary database for writes and reads.

9. CQRS (Command Query Responsibility Segregation)

CQRS is a pattern where the read and write operations are segregated into separate models.

Why Use CQRS?

• Performance: Optimizes queries and commands separately for better performance.
• Scalability: Enables scaling reads and writes independently.
• Complexity Management: Simplifies complex business logic by separating it into distinct models.

Setup

CQRS can be implemented using MediatR for commands and queries in .NET Core.

Example

Problem Statement

You need to manage user data with complex validation logic for commands and optimized read queries.

C# Code Example

In this example:

• CreateUserCommand handles creating a user.
• GetUserQuery handles retrieving user details.

10. Hexagonal Architecture (Ports and Adapters)

Hexagonal Architecture aims to decouple the core logic from external services like databases and APIs, using ports and adapters.

Why Use Hexagonal Architecture?

• Decoupling: Core logic is independent of external dependencies.
• Testability: Easier to test core logic without dependencies.
• Flexibility: Allows switching external services without affecting core logic.

Setup

Define interfaces for external dependencies and implement them using adapters in .NET Core.

Example

Problem Statement

You need to build a payment processing system that can switch between different payment gateways.

C# Code Example

In this example:

• PaymentService uses an IPaymentGateway interface to process payments.
• PayPalPaymentGateway and StripePaymentGateway implement the interface for different payment gateways.

11. Service-Oriented Architecture (SOA)

SOA is a design pattern where services are designed to provide reusable functionality across different applications.

Why Use SOA?

• Reusability: Services can be reused by multiple applications.
• Interoperability: Enables integration with different platforms.
• Modularity: Services are independent and modular.

Setup

In .NET Core, you can create WCF or RESTful services that provide reusable functionalities.

Example

Problem Statement

You need to create a reusable authentication service for multiple applications.

C# Code Example

In this example:

• AuthServiceController exposes authentication endpoints.
• AuthService provides the implementation for authentication logic.

12. Onion Architecture

Onion Architecture addresses the common issues of tight coupling and separation of concerns by structuring an application around its domain model.

Why Use Onion Architecture?

• Decoupling: Separates business logic from infrastructure and UI layers.
• Testability: Core logic can be tested without dependencies.
• Maintainability: Changes in infrastructure do not affect business logic.

Setup

Structure your application with layers such as Core, Application, Infrastructure, and UI.

Example

Problem Statement

You need to build an e-commerce system that maintains a clear separation between business logic and other layers.

C# Code Example

In this example:

• Core layer defines the domain model (Product) and repository interface.
• Application layer contains business logic (ProductService).
• Infrastructure layer implements data access (ProductRepository).
• UI layer exposes endpoints (ProductsController).

13. Clean Architecture

Clean Architecture, proposed by Robert C. Martin (Uncle Bob), focuses on a clear separation between core business logic and other components, making the system flexible and maintainable.

Why Use Clean Architecture?

• Independence: Business rules can be tested without UI, database, or any external components.
• Flexibility: Makes the application easier to change, adapt, and maintain.
• Separation of Concerns: Each layer has distinct responsibilities.

Setup

Define the core logic in the innermost layer and infrastructure in the outermost layer.

Example

Problem Statement

You need to design a flexible application that handles customer orders with clear separation between layers.

C# Code Example

In this example:

• Core layer defines the domain model (Order), repository interface (IOrderRepository), and use case (CreateOrderUseCase).
• Infrastructure layer implements the repository (OrderRepository).
• UI layer exposes endpoints (OrdersController).

14. Event Sourcing

Event Sourcing persists the state of an entity as a sequence of events, rather than storing the current state.

Why Use Event Sourcing?

• Auditability: Complete history of changes is preserved.
• Flexibility: Rebuild the state of an entity at any point in time.
• Scalability: Event streams can be partitioned and scaled.

Setup

Implement event sourcing by defining events and replaying them to reconstruct state.

Example

Problem Statement

You need to implement a system where the entire history of bank account transactions is preserved and can be replayed.

C# Code Example

In this example:

• BankAccountEvent is the base class for events.
• BankAccount aggregate maintains state by applying events.
• EventStoreRepository stores and retrieves events.

Conclusion ??

By thoughtfully applying above explained patterns, along with core principles like SOLID and async programming, you can craft .NET applications that are performant, maintainable, and a joy to work with. As you tackle new challenges and build sophisticated systems, keep these architectural approaches in mind - they'll help you navigate the complexities of software design with confidence and finesse! ??