如何触发TreeView LostFocus事件

我有一个这样的TreeView:

        <TreeView LostFocus="treeView_LostFocus">
            <TreeViewItem Selected="treeViewItem_select"/>
        </TreeView>

它总是触发事件treeView_LostFocus首先当我选择不同的项目在TreeViewItem使用treeViewItem_select。如何只在TreeView失焦时触发失焦事件，而不是在触发treeViewItem_select之前触发失焦事件?

ps: make e.Handle = true in the end of treeViewItem_select seems not work.

private void treeView_LostFocus(object sender, RoutedEventArgs e)
{
    var tv = sender as TreeView;
    if (tv.IsKeyboardFocusWithin == false)
    {
        //Your code
    }
}