Checking if a RoutedEvent has any handlers
- by AK
I've got a custom Button class, that always performs the same action when it gets clicked (opening a specific window). I'm adding a Click event that can be assigned in the button's XAML, like a regular button.
When it gets clicked, I want to execute the Click event handler if one has been assigned, otherwise I want to execute the default action. The problem is that there's apparently no way to check if any handlers have been added to an event.
I thought a null check on the event would do it:
if (Click == null)
{
DefaultClickAction();
}
else
{
RaiseEvent(new RoutedEventArgs(ClickEvent, this));;
}
...but that doesn't compile. The compiler tells me that I can't do anything other than += or -= to an event outside of the defining class, event though I'm trying to do this check INSIDE the defining class.
I've implemented the correct behavior myself, but it's ugly and verbose and I can't believe there isn't a built-in way to do this. I must be missing something.
Here's the relevant code:
public class MyButtonClass : Control
{
//...
public static readonly RoutedEvent ClickEvent =
EventManager.RegisterRoutedEvent("Click",
RoutingStrategy.Bubble,
typeof(RoutedEventHandler),
typeof(MyButtonClass));
public event RoutedEventHandler Click
{
add { ClickHandlerCount++; AddHandler(ClickEvent, value); }
remove { ClickHandlerCount--; RemoveHandler(ClickEvent, value); }
}
private int ClickHandlerCount = 0;
private Boolean ClickHandlerExists
{
get { return ClickHandlerCount > 0; }
}
//...
}
