WPF：TreeViewItem向上和向下移动

Question

我正在尝试在选择中上下移动 TreeViewItem。尝试了所有在线论坛，但建议方式对我不起作用。任何人都可以帮忙。下面是我为Treecreation编写的代码。

XAML：

  <TreeView Name="treeFileSystem" TreeViewItem.Selected="TreeViewItemSelected">
      <TreeViewItem Header="Suite"  Name="MYTree" Tag="hi"  IsExpanded="True">
          <TreeViewItem    Name="treeFileSystem1" />                              
       </TreeViewItem>
  </TreeView>

CODE：

private void TestsTreeViewPageFunction_Loaded(object sender, RoutedEventArgs e)
        {
            this.MYTree.Items.Clear();

            this.MYTree.ContextMenu = AddContexMenu("Suite");

            for (int j = 1; j < 5; j++)
            {
                TreeViewItem Case = new TreeViewItem();

                Case.ContextMenu = AddContexMenu("Case");
                Case.Header = "Case "+j.ToString();
                Case.IsExpanded = true;
                for (int i = 0; i < 5; i++)
                {
                    Case.Items.Add(Trythis(i));
                }
                this.MYTree.Items.Add(Case);
            }

        }

private TreeViewItem Trythis(int i)
        {
            TreeViewItem Step = new TreeViewItem();

            Step.Header = "Steps " + i.ToString();
            Step.ContextMenu = AddContexMenu("Step");

            return Step;          
        }