ASP.net，ASP.net 省市级联（用户控件）适用用framework3.5以上版本

ASCX页面

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="ProvinceCity.ascx.cs"
    Inherits="ProvinceCity" %>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        省份：<asp:DropDownList ID="ddlProvince" Width="60px" AutoPostBack="true" runat="server"
            OnSelectedIndexChanged="ddlProvince_SelectedIndexChanged">
        </asp:DropDownList>
        &nbsp; 城市：<asp:DropDownList ID="ddlCity" Width="60px" runat="server">
        </asp:DropDownList>
    </ContentTemplate>
</asp:UpdatePanel>

ASP.net。 

CS页面

javaweb省市级联。using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Collections;

public partial class ProvinceCity : System.Web.UI.UserControl
{
    /// <summary>
    /// 得到或设置省份下拉框的值
    /// </summary>
    public string Province
    {
        get { return ddlProvince.SelectedValue; }
        set { ddlProvince.SelectedValue = value; CreateCityItem(); }
    }

    /// <summary>
    /// 得到或设置城市下拉框的值
    /// </summary>
    public string City
    {
        get { return ddlCity.SelectedValue; }
        set { ddlCity.SelectedValue = value; }
    }

    public void Bind()
    {
        CreateProvinceItem();
        CreateCityItem();
    }

jquery省市级联、    /// <summary>
    /// 绑定城市的值
    /// </summary>
    /// <returns></returns>
    public void CreateCityItem()
    {
        ArrayList cityOptions = new ArrayList();
        string item = string.Empty;
        switch (ddlProvince.SelectedItem.Text)
        {
            case "安徽":
                item = "合肥(*),安庆,蚌埠,亳州,巢湖,滁州,阜阳,贵池,淮北,淮化,淮南,黄山,九华山,六安,马鞍山,宿州,铜陵,屯溪,芜湖,宣城";
                break;
            case "北京":
                item = "东城,西城,崇文,宣武,朝阳,丰台,石景山,海淀,门头沟,房山,通州,顺义,昌平,大兴,平谷,怀柔,密云,延庆 ";
                break;
            case "重庆":
                item = "万州,涪陵,渝中,大渡口,江北,沙坪坝,九龙坡,南岸,北碚,万盛,双挢,渝北,巴南,黔江,长寿,綦江,潼南,铜梁,大足,荣昌,壁山,梁平,城口,丰都,垫江,武隆,忠县,开县,云阳,奉节,巫山,巫溪,石柱,秀山,酉阳,彭水,江津,合川,永川,南川";
                break;
            case "福建":
                item = "福州(*),福安,龙岩,南平,宁德,莆田,泉州,三明,邵武,石狮,永安,武夷山,厦门,漳州";
                break;
            case "甘肃":
                item = "兰州(*),白银,定西,敦煌,甘南,金昌,酒泉,临夏,平凉,天水,武都,武威,西峰,张掖";
                break;
            case "广东":
                item = "广州(*),潮阳,潮州,澄海,东莞,佛山,河源,惠州,江门,揭阳,开平,茂名,梅州,清远,汕头,汕尾,韶关,深圳,顺德,阳江,英德,云浮,增城,湛江,肇庆,中山,珠海";
                break;
            case "广西":
                item = "南宁(*),百色,北海,桂林,防城港,河池,贺州,柳州,钦州,梧州,玉林";
                break;
            case "贵州":
                item = "贵阳(*),安顺,毕节,都匀,凯里,六盘水,铜仁,兴义,玉屏,遵义";
                break;
            case "海南":
                item = "海口(*),儋县,陵水,琼海,三亚,通什,万宁";
                break;
            case "河北":
                item = "石家庄(*),保定,北戴河,沧州,承德,丰润,邯郸,衡水,廊坊,南戴河,秦皇岛,唐山,新城,邢台,张家口";
                break;
            case "黑龙江":
                item = "哈尔滨(*),北安,大庆,大兴安岭,鹤岗,黑河,佳木斯,鸡西,牡丹江,齐齐哈尔,七台河,双鸭山,绥化,伊春";
                break;
            case "河南":
                item = "郑州(*),安阳,鹤壁,潢川,焦作,济源,开封,漯河,洛阳,南阳,平顶山,濮阳,三门峡,商丘,新乡,信阳,许昌,周口,驻马店";
                break;
            case "香港":
                item = "香港,九龙,新界";
                break;
            case "湖北":
                item = "武汉(*),恩施,鄂州,黄冈,黄石,荆门,荆州,潜江,十堰,随州,武穴,仙桃,咸宁,襄阳,襄樊,孝感,宜昌";
                break;
            case "湖南":
                item = "长沙(*),常德,郴州,衡阳,怀化,吉首,娄底,邵阳,湘潭,益阳,岳阳,永州,张家界,株洲";
                break;
            case "江苏":
                item = "南京(*),常熟,常州,海门,淮安,江都,江阴,昆山,连云港,南通,启东,沭阳,宿迁,苏州,太仓,泰州,同里,无锡,徐州,盐城,扬州,宜兴,仪征,张家港,镇江,周庄";
                break;
            case "江西":
                item = "南昌(*),抚州,赣州,吉安,景德镇,井冈山,九江,庐山,萍乡,上饶,新余,宜春,鹰潭";
                break;
            case "吉林":
                item = "长春(*),白城,白山,珲春,辽源,梅河,吉林,四平,松原,通化,延吉";
                break;
            case "辽宁":
                item = "沈阳(*),鞍山,本溪,朝阳,大连,丹东,抚顺,阜新,葫芦岛,锦州,辽阳,盘锦,铁岭,营口";
                break;
            case "澳门":
                item = "澳门";
                break;
            case "内蒙古":
                item = "呼和浩特(*),阿拉善盟,包头,赤峰,东胜,海拉尔,集宁,临河,通辽,乌海,乌兰浩特,锡林浩特";
                break;
            case "宁夏":
                item = "银川(*),固源,石嘴山,吴忠";
                break;
            case "青海":
                item = "西宁(*),德令哈,格尔木,共和,海东,海晏,玛沁,同仁,玉树";
                break;
            case "山东":
                item = "济南(*),滨州,兖州,德州,东营,菏泽,济宁,莱芜,聊城,临沂,蓬莱,青岛,曲阜,日照,泰安,潍坊,威海,烟台,枣庄,淄博";
                break;
            case "上海":
                item = "崇明,黄浦,卢湾,徐汇,长宁,静安,普陀,闸北,虹口,杨浦,闵行,宝山,嘉定,浦东,金山,松江,青浦,南汇,奉贤 ";
                break;
            case "山西":
                item = "太原(*),长治,大同,候马,晋城,离石,临汾,宁武,朔州,忻州,阳泉,榆次,运城";
                break;
            case "陕西":
                item = "西安(*),安康,宝鸡,汉中,渭南,商州,绥德,铜川,咸阳,延安,榆林";
                break;
            case "四川":
                item = "成都(*),巴中,达川,德阳,都江堰,峨眉山,涪陵,广安,广元,九寨沟,康定,乐山,泸州,马尔康,绵阳,南充,内江,攀枝花,遂宁,汶川,西昌,雅安,宜宾,自贡,资阳";
                break;
            case "台湾":
                item = "台北(*),基隆,台南,台中,高雄,屏东,南投,云林,新竹,彰化,苗栗,嘉义,花莲,桃园,宜兰,台东,金门,马祖,澎湖";
                break;
            case "天津":
                item = "天津(*),和平,东丽,河东,西青,河西,津南,南开,北辰,河北,武清,红挢,塘沽,汉沽,大港,宁河,静海,宝坻,蓟县";
                break;
            case "新疆":
                item = "乌鲁木齐(*),阿克苏,阿勒泰,阿图什,博乐,昌吉,东山,哈密,和田,喀什,克拉玛依,库车,库尔勒,奎屯,石河子,塔城,吐鲁番,伊宁";
                break;
            case "西藏":
                item = "拉萨(*),阿里,昌都,林芝,那曲,日喀则,山南";
                break;
            case "云南":
                item = "昆明(*),大理,保山,楚雄,东川,个旧,景洪,开远,临沧,丽江,六库,潞西,曲靖,思茅,文山,西双版纳,玉溪,中甸,昭通";
                break;
            case "浙江":
                item = "杭州(*),安吉,慈溪,定海,奉化,海盐,黄岩,湖州,嘉兴,金华,临安,临海,丽水,宁波,瓯海,平湖,千岛湖,衢州,江山,瑞安,绍兴,嵊州,台州,温岭,温州,余姚,舟山";
                break;
            case "海外":
                item = "欧洲,北美,南美,亚洲,非洲,大洋洲";
                break;
            default:
                item = "";
                break;
        }
        string[] temp = item.Split(',');
        ddlCity.Items.Insert(0, "选择市");
        for (int i = ddlCity.Items.Count - 1; i >= 1; i--)
        {
            ddlCity.Items.RemoveAt(ddlCity.Items.Count - 1);
        }

        for (int i = 1; i <= temp.Length; i++)
        {
            ddlCity.Items.Insert(i, temp[i - 1].ToString());
        }
    }

    /// <summary>
    /// 绑定省份的值
    /// </summary>
    /// <returns></returns>
    public void CreateProvinceItem()
    {
        string[] item = "选择省,北京,上海,重庆,安徽,福建,甘肃,广东,广西,贵州,海南,河北,黑龙江,河南,香港,湖北,湖南,江苏,江西,吉林,辽宁,澳门,内蒙古,宁夏,青海,山东,山西,陕西,四川,台湾,天津,新疆,西藏,云南,浙江,海外".Split(',');
        for (int i = 0; i < item.Length; i++)
        {
            ddlProvince.Items.Insert(i, item[i].ToString());
        }
    }

    protected void ddlProvince_SelectedIndexChanged(object sender, EventArgs e)
    {
        CreateCityItem();
    }
}