In the ContextMenu_Opened function i put the following code.
93 var cMenu = sender as ContextMenu;
94 var tbase = (cMenu.PlacementTarget as StackPanel).DataContext as BasicTreeViewBase;
95 tbase.IsSelected = true;
Which will set my selected item to true. The BasicTreeViewBase is a ViewModdle object baised off of the code found at TreeViewWithViewModel and is rather simple.