MediatR is a popular open-source .NET library that implements the Mediator pattern to provide simple and flexible request/response handling, command processing, and event notifications while promoting loose coupling between application components.
https://mediatr.app/
Mediatr

Product Information

Updated:Nov 9, 2024

What is Mediatr

MediatR is a lightweight but powerful library developed by Jimmy Bogard for implementing the Mediator design pattern in .NET applications. It acts as a middleware that helps decouple application components by routing requests, commands, queries and notifications between different parts of the system without them having direct dependencies on each other. The library is particularly useful for implementing the Command Query Responsibility Segregation (CQRS) pattern and managing in-process messaging in a clean and maintainable way.

Key Features of Mediatr

MediatR is a lightweight .NET library that implements the Mediator pattern, providing a simple way to handle in-process messaging with no dependencies. It supports request/response patterns, commands, queries, notifications, and events, both synchronously and asynchronously. The library enables loose coupling between components and helps implement CQRS (Command Query Responsibility Segregation) architecture in .NET applications.
Pipeline Behaviors: Supports middleware-like behaviors for cross-cutting concerns such as logging, validation, and caching, allowing developers to add functionality without modifying existing code
Automatic Handler Discovery: Automatically identifies and registers handlers in the application, reducing the need for explicit configuration and simplifying setup
Multiple Message Types: Supports various types of messages including request/response, commands, queries, notifications and events with intelligent dispatching via C# generic variance
Cross-Platform Compatibility: Works across different .NET platforms including .NET Framework 4.6.1 and netstandard2.0, making it versatile for various project types

Use Cases of Mediatr

Web API Development: Ideal for building clean, maintainable ASP.NET Core APIs by separating business logic from controllers and implementing CQRS pattern
Enterprise Applications: Helps manage complexity in large-scale enterprise applications by organizing code into feature-focused modules with loose coupling
Event-Driven Systems: Facilitates building event-driven architectures by handling notifications and events within the application

Pros

Promotes clean architecture and separation of concerns
Reduces coupling between application components
Simple to implement and integrate with minimal setup

Cons

Can introduce performance overhead in high-throughput scenarios
May add unnecessary complexity for smaller applications
Limited to in-process communication only

How to Use Mediatr

Install Required NuGet Packages: Add the MediatR and MediatR.Extensions.Microsoft.DependencyInjection NuGet packages to your .NET project
Configure MediatR in Startup: Add MediatR to the service collection in ConfigureServices method using services.AddMediatR() to register handlers automatically
Create Request Class: Create a class that implements either IRequest (for commands with no return value) or IRequest<T> (for queries that return data)
Create Handler Class: Create a handler class that implements IRequestHandler<TRequest> or IRequestHandler<TRequest,TResponse> and implements the Handle method
Inject IMediator: Inject IMediator interface into your controllers or services where you need to send requests
Send Requests: Use the injected IMediator to send requests using Send() for request/response or Publish() for notifications
Optional: Add Behaviors: Implement pipeline behaviors for cross-cutting concerns like logging, validation, and authorization using IPipelineBehavior<TRequest,TResponse>

Mediatr FAQs

MediatR is a .NET library that implements the mediator pattern, helping to decouple application logic from the presentation layer. It's commonly used in ASP.NET Core applications to manage in-process communication between components.

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