省市县三级联动

先在页面上加了这个：

   < asp:ScriptManager ID = " ScriptManager1 "  runat = " server "  AllowCustomErrorsRedirect = " false "

        EnablePartialRendering = " true "  AsyncPostBackErrorMessage = " cuowu " >

     </ asp:ScriptManager >

实现功能的控件：

   < asp:UpdatePanel ID = " UpdatePanel1 "  runat = " server " >

                         < ContentTemplate >

                             < asp:DropDownList ID = " ddlProvince "  runat = " server " >

                             </ asp:DropDownList >

                             < asp:DropDownList ID = " ddlCity "  runat = " server " >

                             </ asp:DropDownList >

                             < asp:DropDownList ID = " ddlVilliage "  runat = " server " >

                             </ asp:DropDownList >

                             < ajaxToolkit:CascadingDropDown ID = " CascadingDropDown2 "  runat = " server "  TargetControlID = " ddlProvince "

                                ServicePath = " PCAService.asmx "  ServiceMethod = " GetProvinceContents "  Category = " Province "

                                PromptText = " 请选择省份 "  LoadingText = " 省份加载中

" >

                             </ ajaxToolkit:CascadingDropDown >

                             < ajaxToolkit:CascadingDropDown ID = " CascadingDropDown1 "  runat = " server "  ParentControlID = " ddlProvince "

                                ServicePath = " PCAService.asmx "  ServiceMethod = " GetCityContents "  Category = " City "

                                TargetControlID = " ddlCity "  PromptText = " 请选择城市 "  LoadingText = " 城市加载中

" >

                             </ ajaxToolkit:CascadingDropDown >

                             < ajaxToolkit:CascadingDropDown ID = " CascadingDropDown3 "  runat = " server "  Category = " Villiage "

                                LoadingText = " 区县加载中

"  ParentControlID = " ddlCity "  PromptText = " 请选择区县 "  ServiceMethod = " GetViliageContents "

                                ServicePath = " PCAService.asmx "  TargetControlID = " ddlVilliage " >

                             </ ajaxToolkit:CascadingDropDown >

                         </ ContentTemplate >

                     </ asp:UpdatePanel >

App_Code文件夹下 PCAService.cs文件：

using  System;

using  System.Web;

using  System.Collections;

using  System.Web.Services;

using  System.Web.Services.Protocols;

using  System.Web.Script.Services;

using  System.Collections.Generic;

using  System.Collections.Specialized;

using  AjaxControlToolkit;

using  System.Data.SqlClient;

using  System.Data;

using  System.Configuration;

/**/ /// <summary>

///PCAService 的摘要说明

/// </summary>

[WebService(Namespace  =   " http://tempuri.org/ " )]

[WebServiceBinding(ConformsTo  =  WsiProfiles.BasicProfile1_1)]

[System.Web.Script.Services.ScriptService]

public   class  PCAService : System.Web.Services.WebService

{

    public SqlConnection sqlConn;

    public PCAService()

    

{

        //如果使用设计的组件，请取消注释以下行 

        //InitializeComponent(); 

        this.sqlConn = new SqlConnection(ConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString);

    }

    /**//// <summary>

    /// 获取省份数据

    /// </summary>

    /// <param name="knownCategoryValues"></param>

    /// <param name="category"></param>

    /// <returns></returns>

    [WebMethod]

    public CascadingDropDownNameValue[] GetProvinceContents(string knownCategoryValues, string category)

    

{

        List<CascadingDropDownNameValue> provinceList = new List<CascadingDropDownNameValue>();

        sqlConn.Open();

        string strSql = "Select * From Province";

        SqlCommand sqlCmd = new SqlCommand(strSql, sqlConn);

        SqlDataReader dtrProvince = sqlCmd.ExecuteReader();

        while (dtrProvince.Read())

        

{

            provinceList.Add(new CascadingDropDownNameValue(dtrProvince["Name"].ToString(), dtrProvince["Code"].ToString()));

        }

        dtrProvince.Close();

        sqlConn.Close();

        return provinceList.ToArray();

    }

    /**//// <summary>

    /// 获取市数据

    /// </summary>

    /// <param name="knownCategoryValues"></param>

    /// <param name="category"></param>

    /// <returns></returns>

    [WebMethod]

    public CascadingDropDownNameValue[] GetCityContents(string knownCategoryValues, string category)

    

{

        StringDictionary provinceList = CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);

        sqlConn.Open();

        string strSql = "Select * From city Where ProvinceId='" + provinceList["Province"] + "'";

        SqlCommand sqlCmd = new SqlCommand(strSql, sqlConn);

        SqlDataReader dtrCity = sqlCmd.ExecuteReader();

        List<CascadingDropDownNameValue> cityList = new List<CascadingDropDownNameValue>();

        while (dtrCity.Read())

        

{

            cityList.Add(new CascadingDropDownNameValue(dtrCity["Name"].ToString(), dtrCity["code"].ToString()));

        }

        dtrCity.Close();

        return cityList.ToArray();

    }

    /**//// <summary>

    /// 获取乡镇数据

    /// </summary>

    /// <param name="knownCategoryValues"></param>

    /// <param name="category"></param>

    /// <returns></returns>

    [WebMethod]

    public CascadingDropDownNameValue[] GetViliageContents(string knownCategoryValues, string category)

    

{

        StringDictionary cityList = CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);

        sqlConn.Open();

        string strSql = "Select * From area Where CityId='" + cityList["City"] + "'";

        SqlCommand sqlCmd = new SqlCommand(strSql, sqlConn);

        SqlDataReader dtrViliage = sqlCmd.ExecuteReader();

        List<CascadingDropDownNameValue> viliageList = new List<CascadingDropDownNameValue>();

        while (dtrViliage.Read())

        

{

            viliageList.Add(new CascadingDropDownNameValue(dtrViliage["Name"].ToString(), dtrViliage["id"].ToString()));

        }

        dtrViliage.Close();

        return viliageList.ToArray();

    }

}