private void tg_highlightStrategy_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {
     foreach (var item in tg_Area.VertexList)
     {
         HighlightBehaviour.SetHighlightStrategy(item.Value, (HighlightStrategy)tg_highlightStrategy.SelectedItem);
     }
     foreach (var item in tg_Area.EdgesList)
     {
         HighlightBehaviour.SetHighlightStrategy(item.Value, (HighlightStrategy)tg_highlightStrategy.SelectedItem);
     }
 }