treeview控件动态绑定数据库时候，子节点不会出现，断点调试的时候，添加子节点的过程也执行了，但再页面中就是不会显示，以下是我的代码：

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using System.Xml;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            DataView dv = Dview("select * from menu1");
            foreach (DataRowView drv in dv)
            {
                TreeNode tn = new TreeNode();
                tn.Text = drv["text"].ToString();
                tn.Value = drv["bid"].ToString();
                tn.Expanded = true;
                TreeView1.Nodes.Add(tn);
                AddchildNOde(tn);
            }
        }
    }
    private DataView Dview(string query)
    {
        SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["menustr"].ConnectionString);
        SqlDataAdapter da = new SqlDataAdapter(query, conn);
        DataSet ds = new DataSet();
        da.Fill(ds,"tree");
        return ds.Tables["tree"].DefaultView;
    }
    private void AddchildNOde(TreeNode tn)
    {
        int bid = Convert.ToInt32(tn.Value);
        DataView dv = Dview("select * from menu2 where bid='"+bid+"'");
        foreach (DataRowView drv in dv)
        {
            TreeNode ctn = new TreeNode();
            ctn.Text = drv["text"].ToString();
            ctn.Value = drv["cid"].ToString();
            ctn.NavigateUrl = drv["url"].ToString();
            ctn.ChildNodes.Add(ctn);
        }
    }
}

页面中也就是添加了一个treeview控件，没有修改其他的属性，大侠们，求助啊……

在线等……

在线等……

在线等……