Issue: "No service for type 'MediatR.IRequestHandler'"

[AlbertoVPersonal]

Environment

• Windows 11 Pro
• .NET8
• MediatR 12.4.1
• Console app
• All classes are in the same assembly

Issue description

I want to use generic handlers with notifications. Due to I was not able to do it, I have changed to generic requests.
And now I'm getting the below error message.

Issue error message

System.InvalidOperationException: No service for type 'MediatR.IRequestHandler`1[NotificationsMediatR.Notifications.GenericBasicTypeNotification`1[System.String]]' has been registered.

Source code

Handlers

public class LocalMediatR
{
    private static LocalMediatR _instance;

    private IMediator _mediator;

    // ...
}

public class HandlerBaseProperties {
  // ...
}

public class BaseNotification : IRequest {
 // ...
}

internal class GenericBasicTypeNotification<T> : BaseNotification { 
 // ...
}

internal class GenericBaseTypeNoResponseHandler<T> : HandlerBaseProperties, IRequestHandler<GenericBasicTypeNotification<T>>
{
    public async Task Handle(GenericBasicTypeNotification<T> request, CancellationToken cancellationToken) {
       // ...
   }
}

Configure services

//...

// Inject MediatR
services.AddMediatR(cfg => {
    cfg.MaxTypesClosing = 0;
    cfg.RegisterGenericHandlers = true;
    cfg.RegisterServicesFromAssembly(typeof(Startup).Assembly);
});

services.AddSingleton<IMediator, Mediator>();
services.AddTransient<BaseWithoutResponseTopicHandler>();
services.AddTransient(typeof(GenericBaseTypeNoResponseHandler<>));
services.AddTransient<GenericBaseTypeNoResponseHandler<string>>(); // Theoretically it is not needed

//...

Configure method

// set the mediatR
var mediatR = LocalMediatR.GetInstance();
mediatR.SetMediatR(mediator);

Example of use and it generates the error

var notif = new GenericBasicTypeNotification<string>()
{
    Payload = "my value"
};
await LocalMediatR.GetInstance().Mediator.Send(notif);

---

other links read and tests performed

• https://github.com/jbogard/MediatR/wiki
• Question: How to register generic requests #1041
• Handlers for interfaced notifications are not working as expected #1050
• https://stackoverflow.com/questions/73760859/mediatr-generic-handlers/73760945
• https://stackoverflow.com/questions/77862142/how-to-register-generic-type-mediatr-handler/77878919
• https://stackoverflow.com/questions/53895522/add-a-generic-handler-for-send-and-publish-methods-of-the-mediatr-library-in-asp/54041414