Question

I want to subscribe to an EventAggregator event using Reflection, because I am trying to dynamically wire up event subscriptions between Prism modules at runtime. (I’m using Silverlight 5, Prism and MEF).

What I want to achieve is calling _eventAggregator.GetEvent<MyType>().Subscribe(MyAction) in one of my modules, but I am stuck at calling _eventAggregator.GetEvent<MyType>(). How can I proceed from there to call Subscribe(MyAction)?

Say my Event class is public class TestEvent : CompositePresentationEvent<string> { }. I don’t know this at compile time, but I know the Type at runtime.

Here is what I have got so far:

 Type myType = assembly.GetType(typeName); //get the type from string

 MethodInfo method = typeof(IEventAggregator).GetMethod("GetEvent");
 MethodInfo generic = method.MakeGenericMethod(myType);//get the EventAggregator.GetEvent<myType>() method

 generic.Invoke(_eventAggregator, null);//invoke _eventAggregator.GetEvent<myType>();

I would really appreciate a pointer in the right direction.

Answer 1

You can do this without having to worry about the “type” of event you are invoking by using dynamics.

Type eventType = assembly.GetType(typeName);
MethodInfo method = typeof(IEventAggregator).GetMethod("GetEvent");
MethodInfo generic = method.MakeGenericMethod(eventType);
dynamic subscribeEvent = generic.Invoke(this.eventAggregator, null);

if(subscribeEvent != null)
{
    subscribeEvent.Subscribe(new Action<object>(GenericEventHandler));
}

//.... Somewhere else in the class

private void GenericEventHandler(object t)
{
}

Now you really never need to know what the “event type” is.