Just a small reminded for myself. When you are using Publish/Subscribe EventAggregation mechanism provided by PRISM along with Unity to resolve types. It's important to specify the Action method on subscribe to be public.
Example:
TextChangedEvent evt = eventAggregator.GetEvent<TextChangedEvent>();
evt.Subscribe(OnSubscibeForNewText);
///
///
public void OnSubscibeForNewText(string payload)
If it's not public, Unity will have issues resolving the type and you'll see an exception as shown below
Attempt by method 'Microsoft.Practices.Composite.Events.DelegateReference.TryGetDelegate()' to access method 'ModuleA.ViewModel.ModuleAView2VM.OnSubscibeForNewText(System.String)' failed.
Nandri!
Saravana