MiniatR 1.3.0

MiniatR

A lightweight mediator library for .NET. Simple request/response dispatching with pipeline behaviors.

Features

• Minimal API — Just IRequest, IRequestHandler, and ISender
• Pipeline behaviors — Add cross-cutting concerns like logging, validation, caching, retry
• High performance — Compiled expression trees, no runtime reflection after first call
• Full async/cancellation support

Installation

dotnet add package MiniatR

Usage

Define a Request and Handler

public sealed record GetUser(Guid Id) : IRequest<User>;

public sealed class GetUserHandler : IRequestHandler<GetUser, User>
{
    public Task<User> Handle(GetUser request, CancellationToken cancellationToken)
    {
        return Task.FromResult(new User(request.Id, "John Doe"));
    }
}

Register Services

services.AddMiniatR(cfg => cfg
    .RegisterServicesFromAssemblyContaining<GetUser>());

Send Requests

public class UserService(ISender sender)
{
    public Task<User> GetUser(Guid id, CancellationToken ct = default)
        => sender.Send(new GetUser(id), ct);
}

Void Requests

public sealed record DeleteUser(Guid Id) : IRequest;

public sealed class DeleteUserHandler : IRequestHandler<DeleteUser>
{
    public Task Handle(DeleteUser request, CancellationToken cancellationToken)
    {
        return Task.CompletedTask;
    }
}

Pipeline Behaviors

Behaviors wrap request handling for cross-cutting concerns:

public sealed class LoggingBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    where TRequest : notnull
{
    public async Task<TResponse> Handle(
        TRequest request,
        PipelineDelegate<TResponse> next,
        CancellationToken cancellationToken)
    {
        Console.WriteLine($"Handling {typeof(TRequest).Name}");
        var response = await next(cancellationToken);
        Console.WriteLine($"Handled {typeof(TRequest).Name}");
        return response;
    }
}

services.AddMiniatR(cfg => cfg
    .RegisterServicesFromAssemblyContaining<GetUser>()
    .AddBehavior(typeof(LoggingBehavior<,>)));

Configuration Options

services.AddMiniatR(cfg => cfg
    .RegisterServicesFromAssemblyContaining<GetUser>()
    .RegisterServicesFromAssembly(typeof(OtherHandler).Assembly)
    .WithHandlerLifetime(ServiceLifetime.Transient)
    .WithBehaviorLifetime(ServiceLifetime.Scoped)
    .AddBehavior(typeof(LoggingBehavior<,>))
    .AddBehavior<GetUser, User, CachingBehavior>());

Service Lifetimes

Configure lifetimes globally or per-behavior:

services.AddMiniatR(cfg => cfg
    .RegisterServicesFromAssemblyContaining<GetUser>()

    // Global defaults (both default to Scoped)
    .WithHandlerLifetime(ServiceLifetime.Scoped)
    .WithBehaviorLifetime(ServiceLifetime.Scoped)

    // Behaviors using global default
    .AddBehavior(typeof(LoggingBehavior<,>))
    .AddBehavior<ValidationBehavior>()

    // Per-behavior lifetime overrides
    .AddBehavior(typeof(CachingBehavior<,>), ServiceLifetime.Singleton)
    .AddBehavior<MetricsBehavior>(ServiceLifetime.Singleton)
    .AddBehavior<GetUser, User, AuditBehavior>(ServiceLifetime.Transient));

License

MIT