Good question, I don't see a reason for not publishing an event without a payload. There are cases where the fact that an event has been raised is all information you need and want to handle.
There are two options: As it is open source, you can take the Prism source and extract a CompositePresentation event that doesn't take a payload.
I wouldn't do that, but handle Prism as a 3rd party library and leave it as it is. It is good practice to write a Facade for a 3rd party library to fit it into your project, in this case for CompositePresentationEvent
. This could look something like this:
public class EmptyPresentationEvent : EventBase
{
private readonly CompositePresentationEvent<object> _innerEvent;
private readonly Dictionary<Action, Action<object>> _subscriberActions;
public EmptyPresentationEvent()
{
_innerEvent = new CompositePresentationEvent<object>();
_subscriberActions = new Dictionary<Action, Action<object>>();
}
public void Publish()
{
_innerEvent.Publish(null);
}
public void Subscribe(Action action)
{
Action<object> wrappedAction = o => action();
_subscriberActions.Add(action, wrappedAction);
_innerEvent.Subscribe(wrappedAction);
}
public void Unsubscribe(Action action)
{
if (!_subscriberActions.ContainsKey(action)) return;
var wrappedActionToUnsubscribe = _subscriberActions[action];
_innerEvent.Unsubscribe(wrappedActionToUnsubscribe);
_subscriberActions.Remove(action);
}
}
If anything is unclear, please ask.