private static void UnregisterEvent (int eventId, Delegate managedHandler)
{
UnmanagedEventHandler nativeHandler = EventList.RemoveHandler (eventId, managedHandler);
if (nativeHandler == null)
return;
IntPtr t = NativeMethods.surface_get_time_manager (Deployment.Current.Surface.Native);
Events.RemoveHandler (t, eventId, nativeHandler);
}