急！！！在线等待：dropdownlist和treeview组合问题

希望点击dropdownlist后弹出的下拉框里面出现的是一棵树信息，点击树节点后，相应的信息进入dropdownlist，希望好心人帮忙出个主意 --------------------编程问答-------------------- http://topic.csdn.net/u/20100906/14/8f055d33-3961-4768-8b61-b3c0aaf43e96.html --------------------编程问答-------------------- 这个用JS控制也可以，用C#控制也可以，
本人用C#设计一下
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>无标题页</title>
</head>
<body>
    <form id="form1" runat="server">

    <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True">
    <asp:ListItem>1选择</asp:ListItem>
    <asp:ListItem>2选择</asp:ListItem>
    </asp:DropDownList>
    <asp:DropDownList ID="DropDownList2" runat="server">
    </asp:DropDownList>

    </form>
</body>
</html>

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

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string st_name = DropDownList1.SelectedValue.ToString();
        if(Equals(st_name,"1选择"))
        {
            //DropDownList2后台添值
        }
        if (Equals(st_name, "2选择"))
        {
            //DropDownList2后台添值
        }
    }
}
--------------------编程问答-------------------- 学习了我正在找这个·

补充：.NET技术 ,  ASP.NET