MediatR 14.0.0-beta-1

MediatR

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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<,>));
    });

With additional methods for open generics and overloads for explicit service types.

Setting the license key

You can set the license key when registering MediatR:

services.AddMediatR(cfg => 
{
    cfg.LicenseKey = "<license key here>";
})

Or if not using Microsoft.Extensions.DependencyInjection:

Mediator.LicenseKey = "<license key here>";

[!TIP] The license key does not need to be set on client applications (such as Blazor WASM). Turn off the license warning by configuring logging in your logging start configuration: builder.Logging.AddFilter("LuckyPennySoftware.MediatR.License", LogLevel.None);

You can register for your license key at MediatR.io

Showing the top 20 packages that depend on MediatR.

Packages Downloads
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 118
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 123
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 126
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 127
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 129
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 130
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 132
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 133
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 135
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 137
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 139
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 151
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 305
MediatR.Extensions.Microsoft.DependencyInjection
MediatR extensions for ASP.NET Core
 645

.NET Framework 4.6.2

.NET Standard 2.0

.NET 10.0

.NET 9.0

.NET 8.0

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14.1.0 19 03/04/2026
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