Handler not found

I’m trying to register a generic request handler for a generic request, but I’m getting the error below when calling

await _mediator.Send(new ExchangeOrderRequest<ExchangeOrderResponseSuccessEvent>());

System.InvalidOperationException: Handler was not found for request of type MediatR.IRequestHandler2[MyNamespace.ExchangeOrderRequest1[MyNamespace.ExchangeOrderResponseSuccessEvent],MediatR.Unit]. Register your handlers with the container. See the samples in GitHub for examples.

As side note, for giggles, I was able to inject an instance of IRequestHandler<ExchangeOrderRequest< ExchangeOrderResponseSuccessEvent>> into a controller just fine.

// Some assembly scanning, doesn't find my handler
services.AddMediatR(typeof(Startup), typeof(ExchangeOrderRequest), typeof(IDocumentMessage), typeof(OrderExecution.Handler));

// Try to manually add the handler.  Still doesn't find it
services.AddTransient<IRequestHandler<ExchangeOrderRequest<ExchangeOrderResponseSuccessEvent>>, ExchargeOrderRequestHandler<ExchangeOrderResponseSuccessEvent, ExchangeOrderRequest<ExchangeOrderResponseSuccessEvent>>>();




public class ExchargeOrderRequestHandler<TEvent, TRequest> : IRequestHandler<TRequest> 
	where TRequest : ExchangeOrderRequest<TEvent> 
	where TEvent : ExchangeOrderEvent
{
     // Stuff
}`

public class ExchangeOrderRequest<T>: DocumentMessage, IRequest where T: ExchangeOrderEvent
{
     // Stuff
}

public class ExchangeOrderEvent : IEvent
{
      // Stuff
 
		
}

What am I missing here?

[jbogard]

Use a different container, the Microsoft DI container often can’t handle these edge cases, and this is one of them. It can’t handle partially closed generic types.

Otherwise, it might be fixed in the registration side of things, we might be able to forward registrations perhaps?

[WillMarcouiller]

I use Ninject in a .Net 4.8 project and IRequestHandler<,> can’t be resolved through the ContravariantBindingResolver based on MediatR.Examples.Ninject. Could it also be the container in fault?