SierraStack.Mediator

SierraStack.Mediator is a lightweight, extensible in-process mediator for .NET. It provides a clean way to handle request/response messaging, supports pipeline behaviors, and is designed to be a modern, open-source alternative to MediatR — built for performance, simplicity, and testability.

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💬 We're actively working on v0.2.0 and want your input!
📌 Join the conversation in this pinned issue
Let us know what you'd love to see next.

✨ Features

• ✅ Request/Response messaging with IRequest<TResponse> and IRequestHandler<TRequest, TResponse>
• ✅ In-process event publishing via INotification
• ✅ Built-in pipeline behaviors for:
  • Logging
  • Validation (FluentValidation + Custom Abstraction)
  • Retry (Polly)
  • Caching
  • Performance measurement
  • Exception handling
• ✅ Zero external dependencies in core
• ✅ Seamless integration with Microsoft.Extensions.DependencyInjection

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📦 Installation

Install from NuGet:

dotnet add package SierraStack.Mediator
dotnet add package SierraStack.Mediator.Behaviors
dotnet add package SierraStack.Mediator.Extensions.Microsoft

📌 See NuGet Gallery for all available packages.

🚀 Getting Started

1. Define a request

public class Ping : IRequest<string> 
{
    public string Message { get; set; } = "Ping!";
}

2. Define a handler

public class PingHandler : IRequestHandler<Ping, string>
{
    public Task<string> HandleAsync(Ping request, CancellationToken cancellationToken)
    {
        return Task.FromResult($"Pong: {request.Message}");
    }
}

3. Register services (using built-in DI)

services.AddSierraStackMediator(typeof(PingHandler).Assembly);
services.AddSierraStackBehaviors(); // optional

4. Use the mediator

var result = await mediator.SendAsync(new Ping());
// result => "Pong: Ping!"

🔌 Available Behaviors

Install SierraStack.Mediator.Behaviors and register built-in behaviors:

services.AddSierraStackBehaviors();

Or register them individually:

services
    .AddLoggingBehavior()
    .AddValidationBehavior(options =>
    {
        options.ThrowOnFailure = true;
        options.OnFailure = failures =>
        {
            foreach (var failure in failures)
                Console.WriteLine($"Validation failed: {failure.PropertyName} - {failure.ErrorMessage}");
        };
    });

Validation uses a SierraStack-specific abstraction and can integrate with FluentValidation or custom providers.

🧪 Testing

All core components and built-in behaviors are covered with unit tests using xUnit. To run:

dotnet test

📄 License

Licensed under the MIT License.

👋 Contributing

Contributions, suggestions, and ideas are welcome! Please open an issue or pull request to get started.

🔗 Repository

https://github.com/sierrastack/SierraStack

📍 See the full roadmap for upcoming features and plans.

SierraStack.Mediator Benchmarks

These benchmarks use BenchmarkDotNet to measure mediator performance across common scenarios.

Scenario	Mean	Allocated
Simple Request	633 ns	952 B
+ Logging Behavior	TBD	TBD
+ Logging + Retry	TBD	TBD

Run with:

dotnet run -c Release --project SierraStack.Mediator.Benchmarks