How to raise an event Programmatically

Try Hidden_drgdrp_Prop_DragDrop(sender,new DragEventArgs() );

In clarification of other answers:

The event objects have a number of limitations compared to delegate instances used directly. One important limitation is: there is only one way to invoke an event: in the code of the class where the event instance is declared. It is not possible to invoke a event from anywhere else, not even from a derived class, not from a different instance of the same class, regardless to access modifiers or anything else. This is just not allowed.

This limitation does not apply to regular delegate instances used directly, but doing so from other classes or different instances through direct access to a delegate instance would be bad programming practice. That said, this limitation for event is designed for a good reason, as an important fool-proof measure.

By this reason, you should not even try to find any work-around to invoke an event outside its declaring class and its instance, and not try to apply equivalent technique through delegate instances. Instead, you should "move you logic". You should create a separate method to be used in two or more places of you program: one place is a call from the event handler, another one — from somewhere else.

—SA