public void Remove(TreeElementBase elem)
 {
     this.children.Remove(elem);
 }
 public void Append(TreeElementBase elem)
 {
     this.children.Add(elem);
 }
 public void InsertAt(int i, TreeElementBase elem)
 {
     this.children.Insert(i, elem);
 }
 private void TreeElementSelected(TreeElementSelectedEventArgs args)
 {
     this.selectedElement = args.SelectedElement;
     this.selectedElementParent = args.ParentElement;
     this.selectedIndexToParent = args.IndexToParent;
 }