Resolving a Generic with a Generic parameter in Castle Windsor

Question

I am trying to register a type like IRequestHandler1[GenericTestRequest1[T]] which will be implemented by GenericTestRequestHandler`1[T] but I am currently getting an error from Windsor "Castle.MicroKernel.ComponentNotFoundException : No component for supporting the service " Is this type of operation supported? Or is it to far removed from the suppored register( Component.For(typeof( IList<>).ImplementedBy( typeof( List<> ) ) )

below is an example of a breaking test. //////////////////////////////////////////////////////

public interface IRequestHandler{}

public interface IRequestHandler<TRequest> : IRequestHandler where TRequest : Request{} 

public class  GenericTestRequest<T> : Request{} 

public class GenericTestRequestHandler<T> : RequestHandler<GenericTestRequest<T>>{}

[TestFixture]
public class ComponentRegistrationTests{
   [Test]
   public void DoNotAutoRegisterGenericRequestHandler(){

var IOC = new Castle.Windsor.WindsorContainer();
var type = typeof( IRequestHandler<> ).MakeGenericType( typeof( GenericTestRequest<> ) );
IOC.Register( Component.For( type ).ImplementedBy( typeof( GenericTestRequestHandler<> ) ) );

var requestHandler = IoC.Container.Resolve( typeof(IRequestHandler<GenericTestRequest<String>>));

Assert.IsInstanceOf <IRequestHandler<GenericTestRequest<String>>>( requestHandler );
Assert.IsNotNull( requestHandler );
}
}

Answer 1

I think the problem here is that the service type is not a generic type definition, while the implementation type is. The following tests all pass, which proves this:

[Test]
public void ServiceIsNotGenericTypeDefinition() {
    var service = typeof(IRequestHandler<>).MakeGenericType(typeof(GenericTestRequest<>));
    Assert.IsFalse(service.IsGenericTypeDefinition);
}

[Test]
public void ImplementationIsGenericTypeDefinition() {
    var implementation = typeof (GenericTestRequestHandler<>);
    Assert.IsTrue(implementation.IsGenericTypeDefinition);
}

[Test]
[ExpectedException(typeof(InvalidOperationException))]
public void FillOpenGenericType() {
    var service = typeof(IRequestHandler<>).MakeGenericType(typeof(GenericTestRequest<>));
    service.MakeGenericType(typeof (string));
}

This is because the actual open parameter type on the interface is the "inner" Type, and not the "resulting" type.

So this would be like registering a component with interface ICollection (not the generic ICollection!) and implementation type List<>. When you ask Windsor for ICollection, it doesn't know what type parameter to apply to the implementation type.

In your case it's even worse because you're asking for IRequestHandler<GenericTestRequest<String>> which isn't really registered. (IRequestHandler<GenericTestRequest<>> is)

Hope that was clear...