Question

Is it possible to stop multiple subscribers from subscribing to an event?

I have created a quick example snippet to give my question some context but unfortunately I can’t test it right now because I’m not at my VS machine.

The goal is to:

• Return an empty list if there are no subscribers.
• Return the return value of a single subscriber.
• Throw an exception if more than one subscriber tries to subscribe to the event (this is the crux of the matter).

Is this possible?

public delegate List<IBaseWindow> GetWindowListDelegate();
public static event GetWindowListDelegate GetWindowListEvent;

public List<IBaseWindow> GetWindowList() {

    if (GetWindowListEvent == null) {
        return new List<IBaseWindow>();
    }

    return GetWindowListEvent();
 }

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Note: I’m using .NET 3.5 sp1.

Answer 1

It sounds like you don’t need an event – just expose the delegate itself and allow callers to set the delegate reference on their own.