LiteMediator

A super-lightweight, high-performance alternative to MediatR with 97% test coverage, CI/CD via GitHub Actions, and FluentValidation integration built in.

A lightweight .NET mediator library designed for clean CQRS architecture and fast performance.

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Why LiteMediator?

• Minimal overhead—no external dependencies
• Full Clean Architecture & CQRS support
• Integrates FluentValidation out of the box
• Easy setup—only one line to replace MediatR
• Reliable CI/CD & 97% unit test coverage

✨ Features

Feature	Supported	Description
IMediator.Send()	✅	Core command/request dispatching
IRequest<TResponse>	✅	Request/command abstraction
IRequestHandler<TRequest, TResponse>	✅	Custom request handler logic
IPipelineBehavior<TRequest, TResponse>	✅	Middleware-style behavior support (customizing)
ValidationBehavior (FluentValidation)	✅	Built-in validation using FluentValidation (guide)
INotification + Publish()	✅	Event publishing to multiple handlers
INotificationHandler<T>	✅	Handle published domain events
RegisterHandlersWithMediator()	✅	Auto-registration of all request handlers
RegisterBehaviorsWithMediator()	✅	Auto-registration of pipeline behaviors
AddLiteMediator() extensions	✅	Simplified registration for monoliths & modular monoliths

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🚀 Super Easy MediatR Replacement

✅ All your existing code can stay unchanged:

• Send(request) ✔️
• Publish(notification) ✔️
• IRequest<T> ✔️
• IRequestHandler<T> ✔️
• INotification ✔️
• INotificationHandler<T> ✔️

The only change is in Program.cs / Startup.cs:

// Replace this:
services.AddMediatR(...);

// With this:
services.AddLiteMediator(Assembly.GetExecutingAssembly());

📦 Installation

dotnet add package LiteMediator.Lite

🧩 How to Use

1. Startup Setup
Add services.AddLiteMediator(...) in your Program.cs or Startup.cs.

services.AddLiteMediator(Assembly.GetExecutingAssembly());

Or, Multiple Assemblies

//You can pass multiple assemblies in one go
services.AddLiteMediator(
    typeof(SharedModule.SomeType).Assembly,
    typeof(ModuleA.SomeHandler).Assembly,
    typeof(ModuleB.SomeHandler).Assembly
);

This registers:

• All IRequestHandler(s)
• All IPipelineBehavior(s) (including validation)
• IMediator service

✅ Minimal setup for monolithic or layered apps.

2. Modular Support
Use AddLiteMediatorCore() and AddLiteMediatorModule() for clean modular monoliths.

// Shared module
services.AddLiteMediatorCore(typeof(Shared.AssemblyMarker).Assembly);

// Module1
services.AddLiteMediatorModule(typeof(Module1.AssemblyMarker).Assembly);

// Module2
services.AddLiteMediatorModule(typeof(Module2.AssemblyMarker).Assembly);

Method	Usage
AddLiteMediator()	For monoliths
AddLiteMediatorCore()	Register shared Mediator + Behaviors + Handlers
AddLiteMediatorModule()	Register only module-specific handlers

3. Validation
Just register your FluentValidation validators—they’ll run automatically.

1. Add your validators as normal:

public class MyCommandValidator : AbstractValidator<MyCommand>
{
    public MyCommandValidator()
    {
        RuleFor(x => x.Name).NotEmpty();
    }
}

2. Register them in DI (if not auto-registered):

services.AddValidatorsFromAssembly(Assembly.GetExecutingAssembly());

✅ Your validators will automatically be executed before calling the handler, thanks to the ValidationBehavior.

🔍 Example

1. Sending a Request

public class HelloRequest : IRequest<string>
{
    public string Name { get; set; }
}

public class HelloHandler : IRequestHandler<HelloRequest, string>
{
    public Task<string> Handle(HelloRequest request, CancellationToken cancellationToken)
        => Task.FromResult($"Hello, {request.Name}");
}

var result = await mediator.Send(new HelloRequest { Name = "World" });
// => "Hello, World"

2. Publishing a Notification

public record UserCreated(string Name) : INotification;

public class SendWelcomeEmail : INotificationHandler<UserCreated>
{
    public Task Handle(UserCreated notification, CancellationToken cancellationToken)
    {
        Console.WriteLine($"Welcome email sent to {notification.Name}");
        return Task.CompletedTask;
    }
}

await mediator.Publish(new UserCreated("Alice"));

🛠 Customizing Validation Behavior

LiteMediator includes ValidationBehavior<TRequest, TResponse> using FluentValidation. You can extend it to add logic, or implement IPipelineBehavior to replace it entirely.

1. Extending ValidationBehavior

using FluentValidation;
using LiteMediator;

public class MyCustomValidationBehavior<TRequest, TResponse>
    : ValidationBehavior<TRequest, TResponse>
    where TRequest : IRequest<TResponse>
{
    public MyCustomValidationBehavior(IEnumerable<IValidator<TRequest>> validators)
        : base(validators) { }

    public override async Task<TResponse> Handle(
        TRequest request, 
        RequestHandlerDelegate<TResponse> next, 
        CancellationToken cancellationToken)
    {
        Console.WriteLine("Custom before validation");
        var result = await base.Handle(request, next, cancellationToken);
        Console.WriteLine("Custom after validation");
        return result;
    }
}

2. Implementing IPipelineBehavior from Scratch

using LiteMediator;

public class MyNoOpValidationBehavior<TRequest, TResponse>
    : IPipelineBehavior<TRequest, TResponse>
    where TRequest : IRequest<TResponse>
{
    public Task<TResponse> Handle(
        TRequest request, 
        RequestHandlerDelegate<TResponse> next, 
        CancellationToken cancellationToken)
    {
        Console.WriteLine("Skipping validation");
        return next();
    }
}

Registration:

services.AddTransient(typeof(IPipelineBehavior<,>), typeof(MyNoOpValidationBehavior<,>));

🧪 Testing

• ✅ 97% Unit Test Coverage
• ✅ Integration tests for Send, Publish, validation pipeline
• ✅ GitHub Actions CI/CD

🔧 CI/CD

LiteMediator uses GitHub Actions to automatically:

• Build & Test on every push
• Publish NuGet package on version tag (e.g., v1.0.1)

📁 Folder Structure

src/
  LiteMediator/                # Main library
tests/
  LiteMediator.Tests/          # xUnit integration and unit tests
.github/
  workflows/nuget-publish.yml         # CI/CD pipeline

📃 License

Licensed under the MIT License.

Author

Faojul Ahsan – Senior .NET Backend Engineer passionate about clean architecture, API-first development, and remote collaboration. Seeking global remote opportunities.