The delegate is called asynchronously, and this method returns immediately. You can call this method from any thread, even the thread that owns the control's handle. If the control's handle does not exist yet, this method searches up the control's parent chain until it finds a control or form that does have a window handle. If no appropriate handle can be found, Control.BeginInvoke(Delegate) will throw an exception. Exceptions within the delegate method are considered untrapped and will be sent to the application's untrapped exception handler.

You can call Control.EndInvoke(IAsyncResult) to retrieve the return value from the delegate, if neccesary, but this is not required. Control.EndInvoke(IAsyncResult) will block until the return value can be retrieved.