Mecesoft.MediatR 1.0.3

📦 Mecesoft.MediatR

A lightweight, high-performance MediatR implementation for .NET 9.0, designed with simplicity and efficiency in mind.

✨ Features

• � High Performance: Optimized reflection with caching for minimal runtime overhead.
• 🛡️ Scope Safe: Correctly handles dependency injection scopes, ensuring transaction boundaries and scoped services (like DbContext) work as expected.
• 🧩 Modular: Supports IRequest, IRequestHandler, INotification, and IPipelineBehavior.
• � Safe Scanning: Robust assembly scanning that gracefully handles missing dependencies.
• ✅ Pipeline Support: Easily add cross-cutting concerns like Validation, Logging, or Caching.

🧱 Installation

dotnet add package Mecesoft.MediatR

🔧 Usage

1. Register Services

In your Program.cs or startup configuration:

using Mecesoft.MediatR;

builder.Services.AddMediatR(cfg =>
{
    // Register handlers from the assembly containing 'Program'
    cfg.AddRegisterAssemblies(typeof(Program).Assembly);
    
    // Register pipeline behaviors (optional)
    cfg.AddOpenBehavior(typeof(ValidationBehavior<>));
    cfg.AddOpenBehavior(typeof(LoggingBehavior<>));
});

2. Create Request & Handler

// Define a Request (Command/Query)
public record GetUserByIdQuery(Guid Id) : IRequest<UserDto>;

// Implement the Handler
public class GetUserByIdHandler : IRequestHandler<GetUserByIdQuery, UserDto>
{
    private readonly IUserRepository _repository;

    public GetUserByIdHandler(IUserRepository repository)
    {
        _repository = repository;
    }

    public async Task<UserDto> Handle(GetUserByIdQuery request, CancellationToken cancellationToken)
    {
        var user = await _repository.GetByIdAsync(request.Id);
        return user.ToDto();
    }
}

3. Send Request

Inject ISender into your Controllers or Services:

[ApiController]
[Route("api/[controller]")]
public class UsersController : ControllerBase
{
    private readonly ISender _sender;

    public UsersController(ISender sender)
    {
        _sender = sender;
    }

    [HttpGet("{id}")]
    public async Task<IActionResult> Get(Guid id)
    {
        var result = await _sender.Send(new GetUserByIdQuery(id));
        return Ok(result);
    }
}

⚠️ Important: Middleware & Singleton Services

If you are using ISender inside a Middleware or any Singleton service, you MUST NOT inject it via the constructor. Instead, inject it into the method (Method Injection) to ensure it uses the correct scope.

❌ Wrong (Captive Dependency):

public class MyMiddleware
{
    private readonly ISender _sender;
    public MyMiddleware(RequestDelegate next, ISender sender) // Error!
    {
        _sender = sender;
    }
}

✅ Correct (Method Injection):

public class MyMiddleware
{
    private readonly RequestDelegate _next;
    public MyMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context, ISender sender) // Correct!
    {
        await sender.Send(new MyCommand());
        await _next(context);
    }
}

🏷 License

MIT License – © Mecesoft