MediatorServiceCollectionExtensions

Namespace: RA.Utilities.Dispatcher.Extensions

The MediatorServiceCollectionExtensions class registers the core IDispatcher service with the .NET dependency injection container and applies the compile-time handler registrations produced by the package's source generator.

It provides a simple, one-line extension method, AddMediator, that handles both. The method is written with a C# 14 extension block — it lives inside extension(IServiceCollection services) rather than using the classic this parameter.

// From: /RA.Utilities/Application/RA.Utilities.Dispatcher/Extensions/MediatorServiceCollectionExtensions.cs

public static class MediatorServiceCollectionExtensions
{
    extension(IServiceCollection services)
    {
        public IServiceCollection AddMediator()
        {
            HandlerRegistrations.ApplyAll(services);
            MediatorRegistrations.ApplyAll(services);
            return services;
        }
    }
}

The source generator shipped in the package emits a module initializer for every assembly containing IRequestHandler<,> / IRequestHandler<> / INotificationHandler<> implementations and closed pipeline behaviors. Those initializers queue DI registrations (request handlers scoped, notification handlers and behaviors transient) which AddMediator() then applies — that is why plain handlers need no explicit AddDispatcher / AddNotification call. The generator also emits the Mediator implementation of IDispatcher per assembly — the only dispatcher in the package — and AddMediator() applies its registration. See the Auto Registration and Generated Mediator guides for the assembly-loading guarantee, dispatch strategy, and diagnostics.

Why is this important?

1. Simplifies Setup:

It provides a clean, discoverable way for a developer using your library to get it working. Instead of needing to know the concrete implementation (Mediator), its correct lifetime (Scoped), or the auto-registration queue, they can simply call services.AddMediator().

2. Encapsulation:

It hides the implementation details of the mediator pattern. If you were to change the concrete Mediator class (or the registration mechanics) in the future, developers using your library wouldn't need to change their startup code as long as the extension method remains.

3. Foundation for Features:

This registration is the foundation upon which all other features from RA.Utilities.Dispatcher are built. The source generator and the fluent builders (.AddDispatcher(), .AddNotification()) register the handlers and behaviors, while AddMediator registers the central "dispatcher" that actually processes the requests and notifications — and applies the auto-discovered handlers.

In short, this class is the essential bootstrapping step required to use the CQRS pattern provided by the RA.Utilities.Dispatcher library.