I have 2 handlers using the same form. How do I remove the handlers before adding the new one (C#)?
If you know what those handlers are, just remove them in the same way that you subscribed to them, except with -= instead of +=.
If you don't know what the handlers are, you can't remove them - the idea being that the event encapsulation prevents one interested party from clobbering the interests of another class in observing an event.
EDIT: I've been assuming that you're talking about an event implemented by a different class, e.g. a control. If your class "owns" the event, then just set the relevant variable to null.
If you are working in the form itself, you should be able to do something like:
PseudoCode:
Delegate[] events = Form1.SomeEvent.GetInvokationList();
foreach (Delegate d in events)
{
Form1.SomeEvent -= d;
}
From outside of the form, your SOL.
I realize this question is rather old, but hopefully it will help someone out. You can unregister all the event handlers for any class with a little reflection.
public static void UnregisterAllEvents(object objectWithEvents)
{
Type theType = objectWithEvents.GetType();
//Even though the events are public, the FieldInfo associated with them is private
foreach (System.Reflection.FieldInfo field in theType.GetFields(System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance))
{
//eventInfo will be null if this is a normal field and not an event.
System.Reflection.EventInfo eventInfo = theType.GetEvent(field.Name);
if (eventInfo != null)
{
MulticastDelegate multicastDelegate = field.GetValue(objectWithEvents) as MulticastDelegate;
if (multicastDelegate != null)
{
foreach (Delegate _delegate in multicastDelegate.GetInvocationList())
{
eventInfo.RemoveEventHandler(objectWithEvents, _delegate);
}
}
}
}
}