ajax实现三级联动菜单代码
类似的三级绑定，但在修改信息的时候，绑定然后再提交，下拉框的值总会消失，或者就是回传以后，下拉框的值也会消失，这两天又遇到同样的问题，所以下决心把这个彻底搞定。
本实例用的是jquery+ashx实现。
第一种情况，只有提交的情况
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Area.asp教程x.cs" Inherits="Area" %>
<!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>
<script type="text/网页特效" src="js/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
doChange(null,"province","0");
});
function doChange(id,sub_id,id_value)
{
$("#"+sub_id).empty();
var p_id=id_value;
if(id!=null)
{
p_id=$("#" + id).val();
}
var options="<option value="">请选择</option>";
if(p_id!="")
{
$.getJSON("GetArea.ashx",{pid:p_id},function(data){
$.each(data.items,function(i,item){
options += "<option value="" + item.value + "">" + item.text + "</option>";
});
$("#" + sub_id).append(options);
});
}
else
{
$("#" + sub_id).append(options);
}
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<select name="province" id="province" onchange="doChange('province','city','0','')"></select>省
<select name="city" id="city" onchange="doChange('city','area','0','')"></select>市
<select name="area" id="area"></select>县
</div>
</form>
</body>
</html>
三个select分别用于显示省，市，县
以下是GetArea.ashx代码
<%@ WebHandler Language="C#" Class="GetArea" %>
using System;
using System.Web;
using System.Data;
using GeodonHelper;
public class GetArea : IHttpHandler {
public void ProcessRequest (HttpContext context) {
string startValue = "{"items":[";
string endValue = "]}";
if (context.Request.QueryString["pid"] == null || !ValidateHelper.IsInteger(context.Request.QueryString["pid"].ToString()))
{
context.Response.Write(startValue + "{value:"",text:"参数错误"}" + endValue);
context.Response.End();
}
else
{
int pid = int.Parse(context.Request.QueryString["pid"].ToString());
string middleValue = "";
//DBHelper是我自己写的数据库教程操作类库，目前支持MSSQL MySql，Access，SQlite，此处的代码可以换成你自己的数据库操作代码。
DBHelper sh = DBHelper.CreateInstance();
string sql = "select Id,AreaName from Area where ParentId=@pid";
sh.Params.Add("@pid", pid);
DataTable tb = sh.ExecuteDataTable(sql);
int count = tb.Rows.Count;
if (count == 0)
{
context.Response.Write(startValue + "{value:"",text:"没有数据"}" + endValue);
context.Response.End();
}
else
{
for (int i = 0; i < count; i++)
{
middleValue += ",{value:"" + tb.Rows[i]["Id"].ToString().Trim() + "",text:"" + tb.Rows[i]["AreaName"].ToString().Trim() + ""}";
}
middleValue = middleValue.Substring(1);
context.Response.Write(startValue + middleValue + endValue);
context.Response.End();
}
}
}
public bool IsReusable {
get {
return true;
}
}
}
提交数据的时候用Request["province"],Request["city"],Request["area"]
第二种情况：修改信息先从数据库获取省市县编号，然后绑定三个select，然后再提交数据.
aspx页面
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Edit.aspx.cs" Inherits="Edit" %>
<!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>
<script type="text/javascript" src="js/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
GetProvince();
});
function GetProvince()
{
var province=$("#province");
province.empty();
var options="<option value="">请选择</option>";
$.getJSON("GetArea.ashx",{pid:"0"},function(data){
$.each(data.items,function(i,item){
options += "<option value="" + item.value + "">" + item.text + "</option>";
});
province.append(options);
province.val("<%=province %>");
GetCity();
});
}
function GetCity()
{
var city=$("#city");
city.empty();
var p_id=$("#province").val();
var options="<option value="">请选择</option>";
if(p_id!="")
{
$.getJSON("GetArea.ashx",{pid:p_id},function(data){
$.each(data.items,function(i,item){
options += "<option value="" + item.value + "">" + item.text + "</option>";
});
city.append(options);
city.val("<%=city %>");
GetArea();
});
}
else
{
city.append(options);
GetArea();
}
}
function GetArea()
{
var area=$("#area");
area.empty();
var p_id=$("#city").val();
var options="<option value="">请选择</option>";
if(p_id!="" && p_id!=null)
{
$.getJSON("GetArea.ashx",{pid:p_id},function(data){
$.each(data.items,function(i,item){
options += "<option value="" + item.value + "">" + item.text + "</option>";
});
area.append(options);
area.val("<%=area %>");
});
}
else
{
area.append(options);
}
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<select name="province" id="province" onchange="GetCity()"></select>省
<select name="city" id="city" onchange="GetArea()"></select>市
<select name="area" id="area"></select>县
</div>
<asp:Button ID="btn_submit" runat="server" Text="提交表单"
onclick="btn_submit_Click" /> http://www.zhutiai.com
<br />
<asp:Label ID="lbl_msg" runat="server"></asp:Label>
</form>
</body>
</html>
因为要为每个select赋值，而这个赋值又只能在ajax加载成功之后进行，所以我采取的办法是写三个方法，分别用于加载省，市，县
下面是aspx.cs代码
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 GeodonHelper;
public partial class Edit : System.Web.UI.Page
{
public string province = "", city = "", area = "";
protected void Page_Load(object sender, EventArgs e)
{
if (Request.QueryString["id"] != null)
{
province = "97";
city = "279";
area = "1469";
}
}
protected void btn_submit_Click(object sender, EventArgs e)
{
lbl_msg.Text = Request["province"] + "&" + Request["city"] + "&" + Request["area"];
}
}
ajax加载数据用的还是GetArea.ashx。
补充：asp.net教程,.Net开发 
