How to "Add Above" a row in RadTreeListView when the controls has sort and filter expresions

[Mahdi]

Hi!. I need to add a functionality to my RadTreeListView so when the clicks a context menu "Add Above" a row would be added above the selected row with empty values. My RadTreeListView is bound to a simple self referencing ViewModel which contains children in ObservableCollection. I could do the job when there is no sorting or filtering is applied to the control with adding an object to the parent's ObservableCollection without any problem. But I need to do so event when the control is sorted and filtered.