adding radcontextmenu to RadTreeViewItem.Context

Question

i've created following context menu + menu item.

  RadContextMenu contexMenu = new RadContextMenu();
  RadMenuItem deleteMenuItem = new RadMenuItem();
  RadMenuItem exportMenuItem = new RadMenuItem();
  RadMenuItem exportCsvMenuItem = new RadMenuItem();
  RadMenuItem addToReports = new RadMenuItem() { Header = TranslateComboBoxDB.Translate(VIConstantsStrings.AddToReportTxt).ToString() };
  addToReports.Click += addToReports_Click;

After all processing and all(applying header's n click function)

 contexMenu.Items.Add(addToReports);
 treeViewitem.ContextMenu = contexMenu; //getting error
 e.Handled = true;

for above, treeViewitem is "var treeViewitem = sender as RadTreeViewItem;"

Error i'm getting is:

Cannot convert source type from RadContextMenu to System.....ContextMenu.

so, treeViewitem is a telerik component, and its using a framework element, so how can i add that into the sender object.