dropdownlist 无刷新联动(紧急求助)

大哥们帮我看看下面的代码，不知道为什么不能实现无刷新联动
webform2.aspx.cs 中的代码
protected void Page_Load(object sender, EventArgs e)
    {
        db dbase = new db();
        SqlConnection con = dbase.getConn();
        string sql = @"select * from   ZoneInfoTB";
        SqlDataAdapter da = new SqlDataAdapter(sql, con);
        DataSet ds = new DataSet();
        try
        {
            con.Open();
            da.Fill(ds, "ZoneInfoTB");
            this.DropDownList1.DataSource = ds;
            this.DropDownList1.DataTextField = "DM_Desc";
            this.DropDownList1.DataValueField = "DM_ID";
            this.DropDownList1.DataBind();
            this.DropDownList1.Attributes.Add("onchange", "load(this.options[this.selectedIndex].value)");
        }
        catch (Exception err)
        {        }
        finally
        {
            con.Close();
            con.Dispose();
        }
    }
webform.aspx中的代码
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="WebForm.aspx.cs" Inherits="SCDT_WebForm" %><!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>
    <meta   content="Microsoft   Visual   Studio   .NET   7.1"   name="GENERATOR">   
      <meta   content="C#"   name="CODE_LANGUAGE">   
      <meta   content="JavaScript"   name="vs_defaultClientScript">   
      <meta   content="http://schemas.microsoft.com/intellisense/ie5"   name="vs_targetSchema">   
     <script>   
             function   load(state)
             {   
                var   drp2   =   document.getElementById("DropDownList2");   
                for(var   i   =   0;i<=drp2.options.length   -1;i++)
                {   
                    drp2.remove(i);   
                }   
                var   oHttpReq   =   new   ActiveXObject("MSXML2.XMLHTTP");   
                var   oDoc   =   new   ActiveXObject("MSXML2.DOMDocument");   
                oHttpReq.open("POST",   "webform6.aspx?state="+state,   false);   
                oHttpReq.send("");   
                result   =   oHttpReq.responseText;   
                oDoc.loadXML(result);   
                items   =   oDoc.selectNodes("//city/jghqdatatb");   
                for   (var   item   =  items.nextNode();   item;   item   =   items.nextNode())
                {   
                  var   city   =   item.selectSingleNode("//et").nodeTypedValue;   
                  var   newOption   =   document.createElement("OPTION");   
                  newOption.text   =   city;   
                  newOption.value   =   city;   
                  drp2.options.add(newOption);   
                }   
            }
      </script>  
</head>
<body MS_POSITIONING="flowLayout">       <form   id="Form1"   method="post"   runat="server">   
    <div>
        <asp:DropDownList ID="DropDownList1" runat="server">
        </asp:DropDownList>
        <asp:DropDownList ID="DropDownList2" runat="server">
        </asp:DropDownList></div>
    </form>
</body>
</html>
webform6.aspx.cs 中的代码 protected void Page_Load(object sender, EventArgs e)
    {
        if (Request.QueryString["state"] != null)
        {
            string state = Request.QueryString["state"].ToString();
            db dbase=new db();
            SqlConnection con =dbase.getConn();
            string sql=@"select et  from jghqdatatb   where   InfoFromZoneID  =   '" + state + "'";
            SqlDataAdapter da = new SqlDataAdapter(sql, con);
            DataSet ds = new DataSet();
            da.Fill(ds, "city");
            XmlTextWriter writer = new XmlTextWriter(Response.OutputStream, Response.ContentEncoding);
            writer.Formatting = Formatting.Indented;
            writer.Indentation = 4;
            writer.IndentChar = ' ';
            ds.WriteXml(writer);
            writer.Flush();
            Response.End();
            writer.Close();
        }
    }

解决方案 »

  1.   

    我的xml 文档顶层无效 ，不知道原因,请问谁知道？？？
    XmlTextWriter writer = new XmlTextWriter(Response.OutputStream,Encoding.UTF8);
       writer.Formatting = Formatting.Indented;
       writer.Indentation = 4;
       writer.IndentChar = ' ';
       writer.WriteStartDocument();
       ds.WriteXml(writer);
      

  2.   

    两级联动我觉得没有必要用XMLHTTPRequest对象
    你可以将两个Dropdownlist放到一个updatepanel里面
    后台第一个Dropdownlist的selectchange事件处理函数
    处理第二个Dropdownlist的加载项