Hi

I have a WebDataTree1, I want to expand a particular node with code. But the RootItem can not be fired.
How can I fixed. thx. 

protected void Button1_Click1(object sender, EventArgs e)
{
  NavItem FindItem = WebDataTree1.Nodes.FindNavItemByText(TextBox1.Text, true);
  if (FindItem != null)
  {
    // WebDataTree1.Nodes[0].ExpandChildren(); //  I must add this line at first before function(ExpandChildren)
    ExpandChildren((HierarchicalUIObject)FindItem);
  }
}

private void ExpandChildren(HierarchicalUIObject item)
{
  if (item.ParentItem != null && item.Level >= 0)
  {
    HierarchicalUIObject ChildrenObject = (HierarchicalUIObject)item.ParentItem;
    if (item.Level != 0)
      ((DataTreeNode)ChildrenObject).Nodes[item.Index].ExpandChildren();
    else
       WebDataTree1.Nodes[item.Index].ExpandChildren();

    ExpandChildren(ChildrenObject);
  }
}