private TreeViewItem FileTreeHitTest(MouseButtonEventArgs e)
        {
            var element = FileTree.InputHitTest(e.GetPosition(FileTree)) as DependencyObject;

            while (!(element is TreeViewItem) && element != null)
            {
                element = VisualTreeHelper.GetParent(element);
            }

            var item = (TreeViewItem)element;

            if (item != null)
            {
                item.IsSelected = true;
            }

            return(item);
        }