controlViewType.cs

// Get the control's Type
  Type controlViewType = ((UIElement)control).GetType();
  
  // Dig out the undocumented (yes, I know, it's risky) EventHandlerStore
  // from the control's Type
  PropertyInfo EventHandlersStoreType =
  controlViewType.GetProperty("EventHandlersStore",
  BindingFlags.Instance | BindingFlags.NonPublic);
  
  // Get the actual "value" of the store, not just the reflected PropertyInfo
  Object EventHandlersStore = EventHandlersStoreType.GetValue(tree, null);
  var miGetRoutedEventHandlers = EventHandlersStore.GetType().GetMethod("GetRoutedEventHandlers", BindingFlags.Public | BindingFlags.Instance);
  RoutedEventHandlerInfo[] res = (RoutedEventHandlerInfo[])miGetRoutedEventHandlers.Invoke(EventHandlersStore, new object[] { CheckedTreeViewItem.CheckedEvent });