MediatR

Simple mediator implementation in .NET

In-process messaging with no dependencies.

Supports request/response, commands, queries, notifications and events, synchronous and async with intelligent dispatching via C# generic variance.

Examples in the wiki.

Installing MediatR

You should install MediatR with NuGet:

Install-Package MediatR

Or via the .NET Core command line interface:

dotnet add package MediatR

Either commands, from Package Manager Console or .NET Core CLI, will download and install MediatR and all required dependencies.

Using Contracts-Only Package

To reference only the contracts for MediatR, which includes:

IRequest (including generic variants)
INotification
IStreamRequest

Add a package reference to MediatR.Contracts

This package is useful in scenarios where your MediatR contracts are in a separate assembly/project from handlers. Example scenarios include:

API contracts
GRPC contracts
Blazor

Registering with `IServiceCollection`

MediatR supports Microsoft.Extensions.DependencyInjection.Abstractions directly. To register various MediatR services and handlers:

services.AddMediatR(cfg => cfg.RegisterServicesFromAssemblyContaining<Startup>());

or with an assembly:

services.AddMediatR(cfg => cfg.RegisterServicesFromAssembly(typeof(Startup).Assembly));

This registers:

IMediator as transient
ISender as transient
IPublisher as transient
IRequestHandler<,> concrete implementations as transient
IRequestHandler<> concrete implementations as transient
INotificationHandler<> concrete implementations as transient
IStreamRequestHandler<> concrete implementations as transient
IRequestExceptionHandler<,,> concrete implementations as transient
IRequestExceptionAction<,>) concrete implementations as transient

This also registers open generic implementations for:

INotificationHandler<>
IRequestExceptionHandler<,,>
IRequestExceptionAction<,>

To register behaviors, stream behaviors, pre/post processors:

services.AddMediatR(cfg => {
    cfg.RegisterServicesFromAssembly(typeof(Startup).Assembly);
    cfg.AddBehavior<PingPongBehavior>();
    cfg.AddStreamBehavior<PingPongStreamBehavior>();
    cfg.AddRequestPreProcessor<PingPreProcessor>();
    cfg.AddRequestPostProcessor<PingPongPostProcessor>();
    cfg.AddOpenBehavior(typeof(GenericBehavior<,>));
    });