ASP.NET Ajax级联DropDownList实现代码

<?xmlversion="1.0"encoding="utf-8"?>
<CityServiceSource>
<areaname="中国">
<provinceID="1"provinceID="110000"name="北京市">
<cityCityID="110100"name="市辖区">
<PieceareaPieceareaID="110101"name="东城区" />
<PieceareaPieceareaID="110102"name="西城区" />
<PieceareaPieceareaID="110103"name="崇文区" />
<PieceareaPieceareaID="110104"name="宣武区" />
<PieceareaPieceareaID="110105"name="朝阳区" />
<PieceareaPieceareaID="110106"name="丰台区" />
<PieceareaPieceareaID="110107"name="石景山区" />
<PieceareaPieceareaID="110108"name="海淀区" />
<PieceareaPieceareaID="110109"name="门头沟区" />
<PieceareaPieceareaID="110111"name="房山区" />
<PieceareaPieceareaID="110112"name="通州区" />
<PieceareaPieceareaID="110113"name="顺义区" />
<PieceareaPieceareaID="110114"name="昌平区" />
<PieceareaPieceareaID="110115"name="大兴区" />
<PieceareaPieceareaID="110116"name="怀柔区" />
<PieceareaPieceareaID="110117"name="平谷区" />
</city>
<cityCityID="110200"name="县">
<PieceareaPieceareaID="110228"name="密云县" />
<PieceareaPieceareaID="110229"name="延庆县" />
</city>
</province>
</area>
<areaname="英国">
</area>
<areaname="美国">
</area>
<areaname="日本">
</area>
</CityServiceSource>

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.Web.Script.Services.ScriptService()]
publicclassCityService : System.Web.Services.WebService
{
privatestaticXmlDocument _document; // 用来读取XML数据
privatestaticobject _lock = newobject();// 多线程并发处理
publicstaticXmlDocument Document
{
get
{
lock (_lock)
{
if (_document == null)
{
_document = newXmlDocument();
_document.Load(HttpContext.Current.Server.MapPath("~/App_Data/CityServiceSource.xml"));
}
}
return _document;
}
}
publicstaticstring[] Hierarchy
{
get
{
returnnewstring[] { "area", "province"};// XML数据的层次
}
}
[WebMethod] //一会儿控件会自动调用的web method.这个函数不根据具体情况改变。
public AjaxControlToolkit.CascadingDropDownNameValue[] GetDropDownContents(string knownCategoryValues, string category)
{
StringDictionary knownCategoryValuesDictionary = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
return AjaxControlToolkit.CascadingDropDown.QuerySimpleCascadingDropDownDocument(Document, Hierarchy, knownCategoryValuesDictionary, category);
}
}

<ajaxToolkit:CascadingDropDownID="CascadingDropDown1"runat="server"
ServiceMethod="GetDropDownContents"
ServicePath="~/webservices/cityservice.asmx"TargetControlID="DropDownList1"
Category="area"LoadingText="正在读取..."PromptText="请选择国家">
</ajaxToolkit:CascadingDropDown>
<ajaxToolkit:CascadingDropDownID="CascadingDropDown2"runat="server"
ParentControlID="DropDownList1"ServiceMethod="GetDropDownContentsPageMethod"
TargetControlID="DropDownList2"Category="province"LoadingText="正在读取..."
PromptText="请选择省">
</ajaxToolkit:CascadingDropDown>
<ajaxToolkit:CascadingDropDownID="CascadingDropDown3"runat="server"
ParentControlID="DropDownList2"ServiceMethod="GetDropDownContents"
ServicePath="~/webservices/cityservice.asmx"TargetControlID="DropDownList3"
Category="city"LoadingText="正在读取..."PromptText="请选择城市">
</ajaxToolkit:CascadingDropDown>
<asp:UpdatePanelID="UpdatePanel1"runat="server"UpdateMode="Conditional"RenderMode="inline">
<Triggers>
<asp:AsyncPostBackTriggerControlID="DropDownList3"EventName="SelectedIndexChanged"/>
</Triggers>
</asp:UpdatePanel>