treeview控件添加节点有关问题，大家帮帮忙，

treeview控件添加节点问题，大家帮帮忙，急啊！
树的代码如下
----------------------------------------------------- 
  protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
  {

  if (e.Node.ChildNodes.Count == 0)
  {
  int id = 0;
  id = Convert.ToInt32(e.Node.Value);
  CreateTree(e.Node.ChildNodes, id);
  }
  }

  /// <summary>
  /// 创建树
  /// </summary>
  /// <param name="nodes"></param>
  /// <param name="p_id"></param>
  public void CreateTree(TreeNodeCollection nodes, int p_id)
  {

  nodes.Clear();
  IList<OATree> oaTreeList = oaTreeService.GetOATreeByParentId(p_id);
  if (oaTreeList != null && oaTreeList.Count > 0)
  {
  for (int i = 0; i < oaTreeList.Count; i++)
  {
  OATree oaTreeObj = new OATree();
  oaTreeObj = (OATree)oaTreeList[i];
  nodes.Add(new TreeNode(oaTreeObj.NodeName, oaTreeObj.NodeID.ToString()));
  //nodes[i].CollapseAll(); //折叠树
  nodes[i].SelectAction = TreeNodeSelectAction.Select;
  nodes[i].PopulateOnDemand = true;
  nodes[i].ToolTip = oaTreeObj.NodeName;
  nodes[i].Expand();
  }
  }
  TreeNode tnode = TreeView1.FindNode(hf_nodePath.Value);
  if (tnode != null)
  tnode.Selected = true;
  }
------------------------------------------------
创建出来的树样子如下
tree1
|____
tree2
|____
tree3
|____
也就是有三个树的节点

我想手动加一个顶级节点变成如下效果
treeview
|___tree1
|___tree2
|___tree3
大家帮帮忙。。小弟不才在此谢了！

[解决办法]
在TreeView外部可以通过下面的方式处理：
TreeView.Nodes.Add() - 添加根节点
TreeView.Nodes[i].ChildNodes.Add() - 添加子节点

在你的事件里，自己改一下吧
[解决办法]

C# code

TreeNode tn = TreeView1.Nodes[0];        for (int i = 0; i < ds.Tables[0].Rows.Count; i++)        {            TreeNode YearNode = new TreeNode(ds.Tables[0].Rows[i]["Years"].ToString(), ds.Tables[0].Rows[i]["Years"].ToString());            YearNode.Text = "&nbsp;&nbsp;" + ds.Tables[0].Rows[i]["Years"].ToString() + "年";            for (int j = 1; j < 13; j++)            {                TreeNode MonthNode = new TreeNode(j.ToString(), j.ToString());                MonthNode.Text = "&nbsp;&nbsp;" + j.ToString() + "月";                YearNode.ChildNodes.Add(MonthNode);            }            tn.ChildNodes.Add(YearNode);        }