js 实现二级联动

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前台

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="SetDemo.aspx.cs" Inherits="SetDemo" %>

</head>

</table>

</body>

function Getcity()
{

        if(http_request.readyState==4)//请求完成，发送成功
        {
            //status属性表示HTTP请求的返回状态码，因为XMLHTTP也是请求的一个网页，所以它的含义和传统网页相同，如：200表示正常返回；404表示找不到网页；500表示服务器内部错误。
            if(http_request.status==200)//交易成功
            {
                //在请求正常完成后，responseText表示以文本形式返回请求页面的内容
                 if(http_request.responseText!="")
                 {
                     //new Array(7),可以把7改成一个尽可能大的值，不如说选项中最大的值
                     var myarr=new Array(500);var ResponseText=http_request.responseText;var pos=ResponseText.indexOf(";");var i=0;
                     while(pos!=-1)
                     {

                       var myText=ResponseText.substring(0,pos);
                       if(myText!="")
                       {
                           myarr[i]=myText;
                           i++;
                       }
                       ResponseText=ResponseText.substr(pos+1);
                       pos=ResponseText.indexOf(";");
                       continue;
                          }
                     for(var n=0;n<i;n++)
                     {
                     var value1=myarr[n].substring(0,myarr[n].indexOf("_"));
                     var txt1=myarr[n].substr(myarr[n].indexOf("_")+1);
                     document.getElementById("ddlEquipment").options[n]=new Option(txt1,value1);
                     document.getElementById("ddlEquipment").length=i;
                       }
                 }
                 else
                 {
                     document.getElementById("ddlEquipment").options[0]=new Option("请先选择","0");
                     document.getElementById("ddlEquipment").length=1;
                 }
            }
        }
    }
    </script>

</html>

后台：

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;
using System.Text;
public partial class SetDemo : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
     {

        if (!IsPostBack)
        {

             //省份
                ddlDepartMent.Items.Clear();
                ddlDepartMent.Items.Add(new ListItem("请先选择", "0"));
                ddlDepartMent.Items.Add(new ListItem("湖北省", "HUB"));
                ddlDepartMent.Items.Add(new ListItem("河南省", "HEN"));
                this.ddlDepartMent.Attributes.Add("onchange", "send_request()");
        }
    }
}

新建一般处理程序：

WebHandler Language="C#" Class="GetCity" %>

using System;
using System.Web;
using System.Data.SqlClient;
public class GetCity : IHttpHandler {

    public void ProcessRequest(HttpContext context)
    {
        context.Response.ContentType = "text/plain";
        string CityResult = "";
        string strsql = "Select CityName,Id from InfoCity Where PType='"+type+"'";
        string type = context.Request.QueryString["ProvinceType"].ToString();

sqlconnection con=new sqlconnection();

con.open();

SqlCommand com=new sqlcommand(con,strsql);

      SqlDataReader reader = com.ExecuteReader();

        while (reader.Read())
        {
            CityResult += reader[1] +"_"+ reader[0] + ";";
        }
        context.Response.Write(CityResult);
        reader.Close();

    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }