/// <summary>
/// Called when a diagram item has been deselected.
/// </summary>
/// <param name="arg"></param>
void OnSelectionDeselected(NSelectEventArgs <NDiagramItem> arg)
{
NShape shape = arg.Item as NShape;
if (shape == null)
{
return;
}
// unhook move slaves property changed event
shape.RemoveEventHandler(NShape.MoveSlavesProperty.ValueChangedEvent, new NEventHandler <NValueChangeEventArgs>(OnMoveSlavesPropertyChanged));
// clear hightlights
ClearHighlights();
// destroy property editor
m_PropertyEditorHolder.Content = null;
}