Minimal API with VSA Architecture and CQRS Pattern

This project demonstrates a Minimal API implementation following the Vertical Slice Architecture (VSA) and CQRS (Command Query Responsibility Segregation) pattern. It includes features such as validation using FluentValidation, caching with IMemoryCache, and a Global Exception Handler to provide a clean, scalable, and maintainable API structure.

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Features

1. Minimal API with Vertical Slice Architecture (VSA)
   Each feature (e.g., Books) is organized into its own slice containing:

   • Endpoints
   • Commands/Queries
   • Handlers
   • Validation logic

2. CQRS Pattern
   Segregates read and write operations for better separation of concerns.

3. FluentValidation
   Ensures incoming data is validated consistently and declaratively.

4. Caching with IMemoryCache
   Implements in-memory caching for improving GET endpoint performance.

5. Global Exception Handling
   Provides a centralized mechanism to handle unexpected errors and return meaningful error responses.

6. Pagination
   Built-in pagination for listing endpoints.

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Blazor WASM Demonstration Project

This solution also includes a Blazor WebAssembly demonstration project in the src/BlazorWASM folder. The project showcases a simple CRUD application for managing books with features like listing, creating, editing, and deleting books. It serves as an example of how to use a client-side Blazor application with the Minimal API.

The project includes:

• Razor components for CRUD operations.
• Integration with the Minimal API using an HttpClient.
• Responsive design styled with Bootstrap.

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Tech Stack

• .NET 9
• Entity Framework Core (In Memory) for database operations
• IMemoryCache for caching
• FluentValidation for data validation

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Project Structure

VSAMinimalApi/
│
├── Features/
│   ├── Books/
│   │   ├── CreateBook/
│   │   │   ├── CreateBookCommand.cs
│   │   │   ├── CreateBookHandler.cs
│   │   │   ├── CreateBookValidator.cs
│   │   │   └── CreateBookEndpoint.cs
│   │   ├── DeleteBook/
│   │   │   ├── DeleteBookHandler.cs
│   │   │   └── DeleteBookEndpoint.cs
│   │   ├── GetBook/
│   │   │   ├── GetBookEndpoint.cs
│   │   │   ├── GetBookHandler.cs
│   │   │   └── GetBookResponse.cs
│   │   ├── GetBooks/
│   │   │   ├── GetBooksEndpoint.cs
│   │   │   └── GetBooksHandler.cs
│   │   ├── UpdateBook/
│   │   │   ├── UpdateBookCommand.cs
│   │   │   ├── UpdateBookHandler.cs
│   │   │   ├── UpdateBookEndpoint.cs
│   │   │   └── UpdateBookValidator.cs
│   │   ├── BookEndpoints.cs
│   │
│   └── ExceptionHandling/
│       └── ExceptionHandlingMiddleware.cs
│
├── Database/
│   ├── Models/                # EF Core models
│   └── MyContext.cs           # EF Core DbContext
│
├
├──Program.cs # Application entry point
│          
└── appsettings.json           # Configuration file

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Endpoints

Book Feature

HTTP Method	Endpoint	Description
GET	/books/{id}	Fetch a single book by ID (cached)
GET	/books	Fetch all books with pagination
POST	/books	Create a new book
PUT	/books/{id}	Update an existing book
DELETE	/books/{id}	Delete a book

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Getting Started

Prerequisites

• .NET 9 SDK

Setup

1. Clone the repository:

   git clone https://github.com/salmanhaider14/VSA-MinimalAPIs.git
   cd VSAMinimalApi

2. Install dependencies:

   dotnet restore

3. Run the application:

   dotnet run --project src

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Database

This project is currently configured to use an In-Memory Database for simplicity and demonstration purposes. This allows you to quickly test the application without setting up a database server.

Switching to a Persistent Database

You can configure the application to use a persistent database like SQL Server, PostgreSQL, or SQLite by modifying the MyContext configuration in the Program.cs file.

1. Update the Program.cs file to use a persistent database provider:

   builder.Services.AddDbContext<MyContext>(options =>
       options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

2. Add a connection string to the appsettings.json file:

   {
       "ConnectionStrings": {
           "DefaultConnection": "YourDatabaseConnectionString"
       }
   }

3. Apply migrations:

   dotnet ef migrations add InitialCreate
   dotnet ef database update

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Validation

The project uses FluentValidation for validating requests. Example rules:

• Title: Required and must not exceed 100 characters.
• PublishedDate: Cannot be in the future.
• AuthorName: Required and must not exceed 50 characters.

Validation errors return a structured 400 Bad Request response.

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Caching

• IMemoryCache is used for caching single book retrievals (/books/{id}).
• Cache entries expire after 5 minutes.
• Cache is invalidated after book updates or deletions.

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Global Exception Handling

The ExceptionHandlingMiddleware provides centralized error handling for unexpected exceptions. This middleware ensures:

1. All unhandled exceptions are logged using ILogger.
2. Clients receive a structured 500 Internal Server Error response with a meaningful error message.

To add this middleware, the Program.cs file includes:

app.UseExceptionHandling();

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Pagination

• The GET /books endpoint supports pagination:
  • Query parameters: pageNumber (default: 1), pageSize (default: 10).
  • Example: /books?pageNumber=2&pageSize=5.

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Contributing

All types of contributions are welcome! If you have suggestions, feel free to open a pull request or issue.

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