TreeView控件在动态加载之后，源目录的节点不能显示出来

TreeView控件在动态加载之后，根目录的节点不能显示出来。


后台源码如下：

   /// <summary>
    /// 绑定导航
    /// </summary>
    protected void BindMenu()
    {
        //StringBuilder sb = new StringBuilder();

        //获取登录用户一级权限
        List<SysFunction> srfList = GetSysFunctionByRootDeep(1, 0);
        //end
        if (srfList != null && srfList.Count > 0)
        {
            bubbleSort(srfList);
            
            foreach (SysFunction sf in srfList)
            {
               
                //加载一级菜单

                TreeNode nodeTemp = new TreeNode();
               
                nodeTemp.Text = sf.Name;
                nodeTemp.Value = sf.Name;
                nodeTemp.ImageUrl = "Img/MenuNav/" + sf.ICO;
              
                
             
                //获取登录用户二级权限
                List<SysFunction> srfList2 = GetSysFunctionByRootDeep(2, sf.ID);
                //end
                bubbleSort(srfList2);

              
                foreach (SysFunction sf2 in srfList2)
                {


                    TreeNode ChildNode = new TreeNode();
                    ChildNode.Text = sf2.Name;
                    ChildNode.NavigateUrl = sf.FuncCode + "/" + sf2.FuncCode;
                    nodeTemp.ChildNodes.Add(ChildNode);
                    
               
                }
               
              
                TreeView1.Nodes.Add(nodeTemp); //加入节点
            }
        }
        
    }

前台代码：
   <div id="accordion">
                             <asp:TreeView ID="TreeView1" runat="server" ExpandDepth="0" ForeColor="White" 
                                    ImageSet="Arrows" EnableTheming="False">
                                    <RootNodeStyle ForeColor="Lime"  />
                                    <SelectedNodeStyle ForeColor="White" />