private void RemoveItemFromSelection(MSTreeViewItem newItem)
 {
     if (_selectedItems.Contains(newItem))
     {
         _selectedItems.Remove(newItem);
     }
 }
 private void RemoveItemFromSelection(MultiSelectionTreeViewItem newItem)
 {
     if (_selectedItems.Contains(newItem))
     {
         _selectedItems.Remove(newItem);
     }
     OnTextChanged();
 }