Is there a way to know in VB.NET if a handler has been registered for an event?

Question

In C# I can test for this...

public event EventHandler Trigger;
protected void OnTrigger(EventArgs e)
{
    if (Trigger != null)
        Trigger(this, e);
}
         


        

Answer 1

Yes. null is called "Nothing" in Visual Basic.

If Trigger IsNot Nothing Then

Update

The above answer describes how to check something for null in VB .NET. Unfortunately, events are handled special by the VB.NET compiler.

For this event definition:

Public Event Trigger as EventHandler

You would use this code to check for subscriptions

If TriggerEvent Is Nothing

Notice how VB.Net added a field with the suffix Event to represent the delegate. Have a look here for an explanation.