Why does Wpf TreeView replace action?

Question

I have a wpf TreeView with an mvvm object attached. when I have a child node selected and I reset the parent node, then the parrent node is selected. When I expand the parent again, the parent saves the selection. I want the behavior of Windows Explorer when I destroy the parent, the parent displays highlight, but never gets highlighted, and when I expand it again, the original child shows its selection.

thank