Question

In C# I can check if an event has any listeners:

C# Example:

public static event EventHandler OnClick;

if (OnClick != null)
    OnClick(null, new EventArgs() );

In C++/CLI checking if the event is null is not necessary.

C++/CLI Example:

delegate void ClickDelegate( Object^ sender, MyEventArgs^ e );
event ClickDelegate^ OnClick;

OnClick (sender, args);

BUT, in the project I am working on, I don’t want to construct the MyEventArgs object if there are no listeners.

How do I find out if OnClick has any listeners in C++?

Answer 1

It seems you can’t check that with “trivial events”, like you used, because you don’t have direct access to the underlying field (as with auto-implemented properties in C#).

If you want to do this, you can specify the event’s accessor methods and the backing field explicitly. See How to: Define Event Accessor Methods on how exactly to do that.