MediatR 14.2.0

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<,>));
    });

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);

Auto-discovery via environment variables

If no license key is set in code, MediatR looks for one in environment variables. This is convenient for containerized and cloud environments, and for enterprises that share a single key across many services without code changes:

MEDIATR_LICENSE_KEY – the MediatR-specific license key.
LUCKYPENNY_LICENSE_KEY – a shared key usable across Lucky Penny products (for example, AutoMapper reads the same variable). Because it is shared, the key must be for a license that includes MediatR (a Bundle or MediatR edition); an AutoMapper-only license will not validate here.

The license key is resolved in the following order of precedence, using the first value found:

An explicit value set in code (cfg.LicenseKey or Mediator.LicenseKey).
The MEDIATR_LICENSE_KEY environment variable.
The LUCKYPENNY_LICENSE_KEY environment variable.

No code change is required when using an environment variable—just register MediatR as usual without setting the license key.

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	136
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	140
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	142
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	143
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	144
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	147
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	148
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	150
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	151
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	153
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	168
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	323
MediatR.Extensions.Microsoft.DependencyInjection MediatR extensions for ASP.NET Core	708

Version	Downloads	Last updated
14.2.0	2	07/03/2026
14.1.0	52	03/04/2026
14.0.0	142	12/04/2025
14.0.0-beta-1	67	11/21/2025
13.1.0	85	10/25/2025
13.0.0	494	07/04/2025
12.5.0	152	04/05/2025
12.4.1	582	09/13/2024
12.4.0	341	08/03/2024
12.3.0	162	06/27/2024
12.2.0	269	02/04/2024
12.1.1	138	02/09/2024
12.0.1	151	07/21/2024
12.0.0	33	02/24/2026
11.1.0	152	02/04/2024
11.0.0	290	02/04/2024
10.0.1	217	02/04/2024
10.0.0	158	07/21/2024
9.0.0	150	02/05/2024
8.1.0	146	07/21/2024
8.0.2	147	07/21/2024
8.0.1	138	07/21/2024
8.0.0	138	07/21/2024
7.0.0	143	07/21/2024
6.0.0	156	07/21/2024
5.1.0	134	07/21/2024
5.0.1	139	07/21/2024
5.0.1-alpha-0002	148	07/21/2024
5.0.1-alpha-0001	137	07/21/2024
4.1.0	155	07/21/2024
4.0.1	138	07/21/2024
4.0.0	150	07/21/2024
4.0.0-alpha-0002	160	07/21/2024
4.0.0-alpha	153	07/21/2024
3.0.1	153	07/21/2024
3.0.0	143	07/21/2024
2.1.0	146	07/21/2024
2.1.0-beta-19	143	07/21/2024
2.0.2	126	07/21/2024
2.0.1	138	07/21/2024
2.0.0	129	07/21/2024
2.0.0-beta-005	129	07/21/2024
2.0.0-beta-004	147	07/21/2024
2.0.0-beta-003	135	07/21/2024
2.0.0-beta-002	142	07/21/2024
2.0.0-beta-001	146	07/21/2024
1.0.0	144	07/21/2024
0.5.0	145	07/21/2024
0.4.0	126	07/21/2024
0.3.0	129	07/21/2024
0.2.0	138	07/21/2024
0.1.0	136	07/21/2024

MediatR 14.2.0

Readme

MediatR

Installing MediatR

Using Contracts-Only Package

Registering with IServiceCollection

Setting the license key

Auto-discovery via environment variables

Used By

Dependencies

.NET 10.0

.NET Standard 2.0

.NET 9.0

.NET 8.0

.NET Framework 4.6.2

Versions

Registering with `IServiceCollection`