Question

When we want to pass data to an event subscriber, we use EventArgs (or CustomEventArgs) for this.

.Net provides a build in type EventHandler that uses as a parameter an instance of EventArgs class that is build in as well.

What about cases, when I need to notify a subscriber that some action is over, for example search is over? I don’t want to even use EventArgs, that won’t contain anything.

Is there a build in type for signaling another class, without the need to use empty EventArgs?

Answer 1

You have several options:

1. Use a normal event with an EventHandler and the basic EventArg class – sure the event is empty, but does this do any harm?
2. Make your own delegate and use this with event MyDelegateWithoutParams MyEvent;
3. Use the Observer Pattern with IObservable instead.
4. Let clients pass an Action to you and call this action.

I hope one of these options is to your liking. I use 1 and 4 for this kind of situation (4 mostly, if there will be only one "listener").

PS: I guess 2 won’t conform to the .NET framework guidelines, so maybe that one is not the best idea 😉