Prism - EventAggregator.GetEvent<>.Subscribe() - Using Generics & Contraints

Question

I am having an issue subscribing to events with the event Aggregator that comes as part of the prism framework.

If I use something such as

eventAggregato         


        

Answer 1

MyEvent<IRequest> and MyEvent<Profile> are not the same, so the EventAggregator doesn't see this as the same event. To allow for covariant types, you can fix it with the out modifier in C# 4. Something like this should work:

public interface IMyClass<out T> where T : IRequest { }

public class MyClass<T> : IMyClass<T> where T : IRequest { }

public class MyEvent<TValue> : PubSubEvent<IMyClass<TValue>> where TValue : IRequest { }

Then your event aggregator would look something like:

 _eventAggregator.GetEvent<MyEvent<IRequest>>().Subscribe(Received);

 private void Received(IMyClass<IRequest> obj)
 {

 }

_eventAggregator.GetEvent<MyEvent<IRequest>>().Publish(new MyClass<Profile>());

Does this help?