protected internal virtual void OnShow( 
   bool isVisible
)

{
  // Override the OnShow method of a dockpane to subscribe and unsubscribe to events
  if (isVisible && _eventToken == null) // Subscribe to event when dockpane is visible
  {
    _eventToken = MapSelectionChangedEvent.Subscribe(OnMapSelectionChangedEvent);
  }

  if (!isVisible && _eventToken != null) // Unsubscribe as the dockpane closes.
  {
    MapSelectionChangedEvent.Unsubscribe(_eventToken);
    _eventToken = null;
  }

  void OnMapSelectionChangedEvent(MapSelectionChangedEventArgs obj)
  {
    MessageBox.Show("Selection has changed");
  }
}