~~~~~~~~~~~~~~关于使用WEBSERVICE 做城市联动

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Confirm.aspx.cs" Inherits="admin_Confirm" %><%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %><!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></title>
</head>
<body>
    <form id="form1" runat="server">
    <div> 
        <asp:DropDownList ID="DropDownList1" runat="server">
        </asp:DropDownList>
        <asp:DropDownList ID="DropDownList2" runat="server">
        </asp:DropDownList>
        <cc1:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server">
        </cc1:ToolkitScriptManager>
        <cc1:CascadingDropDown ID="CascadingDropDown1" runat="server" runat="server" TargetControlID="DropDownList1" ServiceMethod="GetProvince" ServicePath="~/CityService.asmx" Category="Province" LoadingText="loading.." PromptText="选择省">
        </cc1:CascadingDropDown>
        <cc1:CascadingDropDown ID="CascadingDropDown2" runat="server" runat="server" TargetControlID="DropDownList2" ServiceMethod="GetCity" ServicePath="~/CityService.asmx" Category="City" LoadingText="loading.." PromptText="选择市">
        </cc1:CascadingDropDown>
       
    </div>
    </form>
</body>
</html>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Collections.Specialized;
using AjaxControlToolkit;
using System.Data;/// <summary>
///CityService 的摘要说明
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
//若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消对下行的注释。 
[System.Web.Script.Services.ScriptService]
public class CityService : System.Web.Services.WebService {    public CityService () {        //如果使用设计的组件，请取消注释以下行 
        //InitializeComponent(); 
    }   [WebMethod]
    [System.Web.Script.Services.ScriptMethod()]
   
    public AjaxControlToolkit.CascadingDropDownNameValue[] GetProvince(string knownCategoryValues, string category)
    {
        List<AjaxControlToolkit.CascadingDropDownNameValue> ListData = new List<AjaxControlToolkit.CascadingDropDownNameValue>();
        DataSet ds = DBHelper.Query("select * from area");
        if (ds == null || ds.Tables.Count <= 0 || ds.Tables[0].Rows.Count <= 0) return null;
        foreach (DataRow row in ds.Tables[0].Rows)
        {
            if (row["parentcode"].ToString() == "0")
            {
                AjaxControlToolkit.CascadingDropDownNameValue value = new AjaxControlToolkit.CascadingDropDownNameValue();
                value.name = row["name"].ToString();
                value.value = row["sz_code"].ToString();
                ListData.Add(value);
            }
        }
        return ListData.ToArray();
    }    [WebMethod]
    [System.Web.Script.Services.ScriptMethod()]
    public AjaxControlToolkit.CascadingDropDownNameValue[] GetCity(string knownCategoryValues, string category)
    {
        StringDictionary sd = CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
        if (sd == null) return null;
        if (sd.ContainsKey("Province") == false) return null;
        int parentID = Int32.Parse(sd["Province"]);
        DataSet ds =DBHelper.Query("select * from area");
        if (ds == null || ds.Tables.Count <= 0 || ds.Tables[0].Rows.Count <= 0) return null;
        List<AjaxControlToolkit.CascadingDropDownNameValue> ListData = new List<CascadingDropDownNameValue>();
        foreach (DataRow row in ds.Tables[0].Rows)
        {
            if (row["ParentCode"].ToString() == parentID.ToString())
            {
                AjaxControlToolkit.CascadingDropDownNameValue value = new AjaxControlToolkit.CascadingDropDownNameValue();
                value.name = row["name"].ToString();
                value.value = row["sz_code"].ToString();
                ListData.Add(value);
            }
        }
        return ListData.ToArray();
    }
}
不太明白为什么结果是这样
省能出现，但城市却不能选择，只处于不可选状态。
数据库是由 parentcode 为0 的话 就得出  省的Name ，
然后市那里就根据选出的省，得出市