用DropDownList控件绑定XML数据实现省市区三级联动

Citys.xml文件格式:

<?xml version="1.0" encoding="utf-8"?>
<PCitys>
<Province pname="安徽省">
    <City cname="蚌埠市">
      <County name="蚌埠市"/>
      <County name="固镇县"/>
      <County name="怀远县"/>
      <County name="五河县"/>
    </City>
    <City cname="巢湖市">
      <County name="巢湖市"/>
      <County name="含山县"/>
      <County name="和县"/>
      <County name="庐江县"/>
      <County name="无为县"/>
    </City>
    <City cname="池州市">
      <County name="池州市"/>
      <County name="东至县"/>
      <County name="青阳县"/>
      <County name="石台县"/>
    </City>
</Province>
</PCitys>
前台显示代码(VS2005的AJAX1.0实现无刷新调数据):

<asp:ScriptManager ></asp:XmlDataSource>
</ContentTemplate></asp:UpdatePanel>

后台代码:

using System;
using System.Data;
using System.Configuration;
using System.Collections;
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;

public partial class EmployeeAdd : System.Web.UI.Page
...{
    protected void Page_Load(object sender, EventArgs e)
    ...{
    }
    protected void ddlProvince_SelectedIndexChanged(object sender, EventArgs e)
    ...{
        ddlCity.Items.Clear();
        ddlCity.Items.Add("地市");
        ddlCity.DataTextField = "cname";
        ddlCity.DataValueField = "cname";
        XmlDataSource2.XPath = "//Province[@pname='" + ddlProvince.SelectedValue + "']/City";
        ddlCounty.Items.Clear();
        ddlCounty.Items.Add("县市");
    }
    protected void ddlCity_SelectedIndexChanged(object sender, EventArgs e)
    ...{
        ddlCounty.Items.Clear();
        ddlCounty.Items.Add("县市");
        ddlCounty.DataTextField = "name";
        ddlCounty.DataValueField = "name";
        XmlDataSource3.XPath = "//Province[@pname='" + ddlProvince.SelectedValue + "']/City[@cname='" + ddlCity.SelectedValue + "']/County";
    }
}