Migrating from MediatR

Coming from OpenMediatR?

AnyMediator was published as OpenMediatR up to 1.5.0. See Upgrading from OpenMediatR at the end of this page.

AnyMediator keeps MediatR's type names, method names and configuration API. Most projects migrate with three mechanical changes and a review of the differences below. You can try the changes on your own files with the converter on the home page.

Why migrate

From version 13, MediatR is dual licensed: the copyleft Reciprocal Public License 1.5, or a commercial license with a license key. AnyMediator is Apache-2.0: free for any use, commercial included, with no key and no threshold. See MediatR alternatives compared for the license details and the other options.

The three changes

1. Swap the package

dotnet remove package MediatR
dotnet add package AnyMediator

If a project referenced MediatR.Contracts, reference AnyMediator.Abstractions instead.

2. Change the namespace

- using MediatR;
- using MediatR.Pipeline;
+ using AnyMediator;
- using MediatR.NotificationPublishers;
+ using AnyMediator.NotificationPublishers;

Everything lives in the AnyMediator namespace, including the pre/post-processor and exception-handler interfaces that MediatR keeps in MediatR.Pipeline. The only exception is the notification publishers (TaskWhenAllPublisher, ForeachAwaitPublisher), in AnyMediator.NotificationPublishers as in MediatR. Global usings work the same way.

3. Change the registration call

- services.AddMediatR(cfg =>
+ services.AddAnyMediator(cfg =>
  {
-     cfg.LicenseKey = "...";
      cfg.RegisterServicesFromAssemblyContaining<Program>();
      cfg.AddOpenBehavior(typeof(LoggingBehavior<,>));
  });

RegisterServicesFromAssembly, RegisterServicesFromAssemblies, RegisterServicesFromAssemblyContaining, AddOpenBehavior, AddBehavior, AddOpenStreamBehavior, AddRequestPreProcessor, AddRequestPostProcessor, AddRequestExceptionHandler, AddRequestExceptionAction, Lifetime, NotificationPublisher, NotificationPublisherType, AutoRegisterRequestProcessors and RequestExceptionActionProcessorStrategy keep their names.

Differences to check

Area	MediatR	AnyMediator
License	RPL-1.5 or commercial from v13	Apache-2.0, free for any use
LicenseKey	Needed under the commercial license; without it, a warning is logged	Does not exist: remove it
Two handlers for one request	The first one found is used	AddAnyMediator throws and names both classes
Publish with several sinks failing	—	Every sink runs, then an AggregateException with every failure
Notification delivery	In-process handlers	In-process handlers, plus any notification sink you add
Custom INotificationPublisher	Publish(IEnumerable<NotificationHandlerExecutor>, INotification, CancellationToken)	Publish(IEnumerable<Func<Task>>, CancellationToken): each delegate runs one handler

Interfaces, method shapes, Send(object), Publish(object), behavior constraints, handlers for base notification types, generic handlers and exceptions from Publish work as in MediatR.

Two handlers for one request

If scanning finds two classes that handle the same request, AddAnyMediator stops with an InvalidOperationException naming both. A test double in a scanned assembly is the usual cause: give it a request type of its own, or leave it out with cfg.TypeEvaluator.

Checklist

1. Replace the package and the namespaces.
2. Replace AddMediatR with AddAnyMediator and remove LicenseKey.
3. Adapt any custom INotificationPublisher to the delegate signature.
4. Start the application: fix any request reported as having two handlers.
5. Run your tests.

Upgrading from AnyMediator 2.0

AnyMediator 2.1 brings AnyMediator in line with MediatR. Review the first four changes before upgrading:

• Publish re-throws handler failures. In 2.0 a failing handler was logged and Publish completed normally. AnyMediator no longer depends on Microsoft.Extensions.Logging.Abstractions.
• Two handlers for one request is a startup error. In 2.0 the first one found was used silently.
• ISender and IPublisher gain Send(object) and Publish(object). A class that implements them by hand, such as a decorator or a test fake, must add the two methods; mocks created by a mocking library are unaffected.
• Handlers for base notification types run. A handler for INotificationHandler<IDomainEvent> now also receives OrderPlaced : IDomainEvent.
• New: generic request and notification handlers, cfg.TypeEvaluator, and the notnull behavior constraint, so behaviors written for MediatR compile unchanged.

Upgrading from OpenMediatR

AnyMediator 2.0.0 is OpenMediatR 1.5.0 under a new name. Behavior is unchanged; only names change.

dotnet remove package OpenMediatR
dotnet add package AnyMediator

OpenMediatR	AnyMediator
OpenMediatR / OpenMediatR.Abstractions packages	AnyMediator / AnyMediator.Abstractions
using OpenMediatR;	using AnyMediator;
using OpenMediatR.NotificationPublishers;	using AnyMediator.NotificationPublishers;
services.AddOpenMediatR(...)	services.AddAnyMediator(...)
OpenMediatRConfiguration	AnyMediatorConfiguration

The converter on the home page applies these changes too.

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AnyMediator is an independent project. It is not affiliated with or endorsed by MediatR, Jimmy Bogard or Lucky Penny Software; MediatR is named only to describe compatibility.