WPF: TreeViewItem move UP and DOWN

I am trying to move up and down the TreeViewItem on Selection. Tried all online forum but the suggest the way is not working for me. Can anyone help please. Below is the code I am writing for Treecreation.

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");
                Cas开发者_JS百科e.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;          
        }