本文主要列举了省市三级联动的DropDownList+Ajax的三种框架(aspnet/Jquery/ExtJs)示例。前段时间需要作一个的Web前端应用，需要用多个框架，一个典型的应用场景是省市三级联动，基于此应用，特将三种主要的ajax框架略作整理，方便有需要的朋友查阅。

在示例之前，我们先设置一个演示数据源，新建一个项目，项目结构如图：

主要文件如下：
AreaModel.cs:
代码如下:
using System;
using System.Collections.Generic;
namespace Downmoon.Framework.Model
{
#region PopularArea
public class Area
{
private string m_Area_ID;
/// <summary>
/// 地区编号
/// </summary>
public string Area_ID
{
get { return m_Area_ID; }
set { m_Area_ID = value; }
}
private string m_Area_Name;
/// <summary>
/// 地区名称
/// </summary>
public string Area_Name
{
get { return m_Area_Name; }
set { m_Area_Name = value; }
}
private double m_Area_Order;
/// <summary>
/// 排序
/// </summary>
public double Area_Order
{
get { return m_Area_Order; }
set { m_Area_Order = value; }
}
private int m_Area_Layer;
/// <summary>
/// 层级
/// </summary>
public int Area_Layer
{
get { return m_Area_Layer; }
set { m_Area_Layer = value; }
}
private string m_Area_FatherID;
/// <summary>
/// 父级ID
/// </summary>
public string Area_FatherID
{
get { return m_Area_FatherID; }
set { m_Area_FatherID = value; }
}
public Area() { }
public Area(string id, string name, double order, int layer, string father)
{
this.Area_ID = id;
this.Area_Name = name;
this.m_Area_Order = order;
this.m_Area_Layer = layer;
this.m_Area_FatherID = father;
}
}
#endregion
}

AreaControl.cs:
代码如下:

using System; 
using System.Collections.Generic; 
using Downmoon.Framework.Model; 
namespace Downmoon.Framework.Controllers 
{ 
public class AreaList : IArea 
{ 
// Area singleton 
private static AreaList instance; 
public static AreaList Instance 
{ 
get 
{ 
if (AreaList.instance == null) 
{ 
AreaList.instance = new AreaList(); 
} 
return AreaList.instance; 
} 
} 
public List<Area> GetAreaList() 
{ 
List<Area> Areas = new List<Area>(); 
Areas.Add(new Area("110000", "北京市", 0, 1, "000000")); 
Areas.Add(new Area("110100", "市辖区", 0, 2, "110000")); 
Areas.Add(new Area("110101", "东城区", 0, 3, "110100")); 
Areas.Add(new Area("110102", "西城区", 0, 3, "110100")); 
Areas.Add(new Area("110103", "崇文区", 0, 3, "110100")); 
Areas.Add(new Area("330000", "浙江省", 0, 1, "000000")); 
Areas.Add(new Area("330100", "杭州市", 0, 2, "330000")); 
Areas.Add(new Area("330200", "宁波市", 0, 2, "330000")); 
Areas.Add(new Area("330102", "上城区", 0, 3, "330100")); 
Areas.Add(new Area("330103", "下城区", 0, 3, "330100")); 
Areas.Add(new Area("330104", "江干区", 0, 3, "330100")); 
Areas.Add(new Area("330105", "拱墅区", 0, 3, "330100")); 
Areas.Add(new Area("330106", "西湖区", 0, 3, "330100")); 
Areas.Add(new Area("330203", "海曙区", 0, 3, "330200")); 
Areas.Add(new Area("330204", "江东区", 0, 3, "330200")); 
Areas.Add(new Area("330205", "江北区", 0, 3, "330200")); 
Areas.Add(new Area("330206", "北仑区", 0, 3, "330200")); 
Areas.Add(new Area("330211", "镇海区", 0, 3, "330200")); 
return Areas; 
} 
public List<Area> GetAreaListFindByParentID(string filter) 
{ 
return GetAreaList().FindAll( 
delegate(Area ar) 
{ 
return ar.Area_FatherID == filter; 
} 
); 
} 
} 
} 
 
Factory.cs 
 代码如下:

using System; 
using System.Collections.Generic; 
//using Downmoon.Framework.Model; 
namespace Downmoon.Framework.Controllers 
{ 
public class Factory 
{ 
public static IArea GetAreaController() 
{ 
return AreaList.Instance; 
} 
} 
} 
 
IArea.cs 
 代码如下:

using System; 
using System.Collections.Generic; 
using System.Text; 
using Downmoon.Framework.Model; 
namespace Downmoon.Framework.Controllers 
{ 
public interface IArea 
{ 
List<Area> GetAreaList(); 
List<Area> GetAreaListFindByParentID(string filterID); 
} 
} 
 
一、基于aspnet自带的Ajax框架，主要好处是与asp.net完全集成，无需写过多的 js。缺点是在framework2下需作一些设置，在Framework 4下无需设置。 
Framework 2： 
需首先在web.config文件中作配置： 
 代码如下:

<?xml version="1.0"?> 
<configuration> 
<configSections> 
<sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35"> 
<sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35"> 
<section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35" requirePermission="false" allowDefinition="MachineToApplication"/> 
<sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35"> 
<section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35" requirePermission="false" allowDefinition="Everywhere" /> 
<section name="profileService" type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35" requirePermission="false" allowDefinition="MachineToApplication" /> 
<section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35" requirePermission="false" allowDefinition="MachineToApplication" /> 
</sectionGroup> 
</sectionGroup> 
</sectionGroup> 
</configSections> 
<system.web> 
<customErrors defaultRedirect="" /> 
<trace mostRecent="true" pageOutput="true" /> 
<pages> 
<controls> 
<add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35"/> 
</controls> 
</pages> 
<compilation> 
<assemblies> 
<add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35" /> 
</assemblies> 
</compilation> 
<httpHandlers> 
<remove verb="*" path="*.asmx"/> 
<add verb="*" path="*.asmx" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35"/> 
<add verb="*" path="*_AppService.axd" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35"/> 
<add verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35" validate="false"/> 
</httpHandlers> 
<httpModules> 
<add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35"/> 
</httpModules> 
</system.web> 
<system.webServer> 
<validation validateIntegratedModeConfiguration="false"/> 
<modules> 
<add name="ScriptModule" preCondition="integratedMode" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35"/> 
</modules> 
<handlers> 
<remove name="WebServiceHandlerFactory-Integrated" /> 
<add name="ScriptHandlerFactory" verb="*" path="*.asmx" preCondition="integratedMode" 
type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35"/> 
<add name="ScriptHandlerFactoryAppServices" verb="*" path="*_AppService.axd" preCondition="integratedMode" 
type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35"/> 
<add name="ScriptResource" preCondition="integratedMode" verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad3e35" /> 
</handlers> 
</system.webServer> 
</configuration> 
 
前台页面： 
 代码如下:

<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="true"> 
</asp:ScriptManager> 
<div> 
<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional"> 
<ContentTemplate> 
<table width="500" border="0" cellpadding="0" cellspacing="2" > 
<tr> 
<td height="25" bgcolor="#EAEAEA" > 
请选择省/市/区： 
</td> 
<td bgcolor="#f7f7f7"> 
<asp:DropDownList ID="dpProvince" runat="server" 
AutoPostBack="true" onselectedindexchanged="dpProvince_SelectedIndexChanged" /> 
<asp:DropDownList ID="dpCity" runat="server" AutoPostBack="true" 
onselectedindexchanged="dpCity_SelectedIndexChanged" /> 
<asp:DropDownList ID="dpArea" runat="server" AutoPostBack="false" 
/> 
</td> 
</tr> 
<tr> 
<td height="25" bgcolor="#EAEAEA" > 
</td> 
<td bgcolor="#f7f7f7"> 
<asp:UpdateProgress ID="UpdateProgress1" runat="server"> 
<ProgressTemplate> 
正在查询，请稍候……………………</ProgressTemplate> 
</asp:UpdateProgress> 
</td> 
</tr> 
</table> 
</ContentTemplate> 
<Triggers> 
<asp:AsyncPostBackTrigger ControlID="dpProvince" EventName="SelectedIndexChanged" /> 
<asp:AsyncPostBackTrigger ControlID="dpCity" EventName="SelectedIndexChanged" /> 
</Triggers> 
</asp:UpdatePanel> 
</div> 
 
Framework 4：与代码完全一样，只是无需在web.config中作配置。 
如图： 

二、基于JQuery1.4.1的Ajax框架，主要好处是与后续版本的asp.net完全集成。 
基于ashx作一个 Request，主要代码： 
 代码如下:

using System; 
using System.Collections.Generic; 
using System.Web; 
using Downmoon.Framework.Controllers; 
using Downmoon.Framework.Model; 
using System.Text; 
namespace dropdown_JQuery14_Net2 
{ 
/// <summary> 
/// Summary description for AjaxRequest 
/// </summary> 
public class AjaxRequest : IHttpHandler 
{ 
public void ProcessRequest(HttpContext context) 
{ 
string Area_FatherID = string.Empty; 
if (context.Request["pid"] != null) 
{ Area_FatherID = context.Request["pid"].ToString(); } 
string parentId = string.Empty; 
//mydbDataContext db = new mydbDataContext(); 
//根据传过来的Value值 进行查询 
//List<ChinaStates> list = db.ChinaStates.Where(c => c.ParentAreaCode == strId).ToList(); 
List<Area> list = Factory.GetAreaController().GetAreaListFindByParentID(Area_FatherID); 
context.Response.ContentType = "application/json"; 
context.Response.ContentEncoding = Encoding.UTF8; 
context.Response.Write(ListToJson(list)); 
context.Response.End(); 
} 
public string ListToJson(List<Area> list) 
{ 
StringBuilder sb = new StringBuilder(); 
if (list != null) 
{ 
sb.Append("["); 
for (int i = 0; i < list.Count; i++) 
{ 
sb.Append("{"); 
sb.Append("\"Area_ID\":\"" + list[i].Area_ID + "\","); 
sb.Append("\"Area_Name\":\"" + list[i].Area_Name + "\""); 
//sb.Append("\"Area_FatherID\":\"" + list[i].Area_FatherID + "\""); 
if (i != list.Count - 1) 
{ 
sb.Append("},"); 
} 
} 
} 
sb.Append("}"); 
sb.Append("]"); 
return sb.ToString(); 
} 
public bool IsReusable 
{ 
get 
{ 
return false; 
} 
} 
} 
} 
 
前台：aspx 
 代码如下:

<!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> 
<mce:style type="text/css"><!-- 
#dpCity 
{ 
display: none; 
position: relative; 
} 
#dpArea 
{ 
display: none; 
position: relative; 
} 
--></mce:style><style type="text/css" mce_bogus="1"> #dpCity 
{ 
display: none; 
position: relative; 
} 
#dpArea 
{ 
display: none; 
position: relative; 
} 
</style> 
<mce:script language="javascript" type="text/javascript" src="Scripts/jquery-1.4.1.js" mce_src="Scripts/jquery-1.4.1.js"></mce:script> 
</head> 
<body> 
<form id="form1" runat="server"> 
<div> 
请选择省/市/区： <asp:DropDownList ID="dpProvince" runat="server" /> 
<asp:DropDownList ID="dpCity" runat="server"> 
</asp:DropDownList> 
<asp:DropDownList ID="dpArea" runat="server" AutoPostBack="false" /> 
</div> 
<mce:script language="javascript" type="text/javascript"><!-- 
$(function () { 
var $dp1 = $("#dpProvince"); 
var $dp2 = $("#dpCity"); 
var $dp3 = $("select[name$=dpArea]"); 
$dp1.focus(); 
//alert($dpCity); 
loadAreas("000000", "0"); 
$dp1.bind("change keyup", function () { 
if ($(this).val() != "") { 
//alert($("select option:selected").val()); 
//loadAreas($("select option:selected").val(), "1"); 
var strPid = $dp1.attr("value"); //获取城市 
loadAreas(strPid, "1"); 
$dp2.fadeIn("slow"); 
} else { 
$dp2.fadeOut("slow"); 
} 
}); 
$dp2.bind("change keyup", function () { 
var strCId = $dp2.attr("value"); //获取城市 
if ($(this).val() != "") { 
loadAreas(strCId, "2"); 
$dp3.fadeIn("slow"); 
} else { 
$dp3.fadeOut("slow"); 
} 
}); 
}); 
function loadAreas(selectedItem, level) { 
$.getJSON("AjaxRequest.ashx?pid=" + selectedItem, function (data) { 
switch (level) { 
case "0": 
$("#dpProvince").html(""); 
$("#dpProvince").append("<option value='' selected='selected'>请选择...</option>"); 
for (var i = 0; i < data.length; i++) { 
$("#dpProvince").append($("<option></option>").val(data[i].Area_ID).html(data[i].Area_Name)); 
}; 
break; 
case "1": 
$("#dpCity").html(""); 
$("#dpCity").append("<option value='' selected='selected'>请选择...</option>"); 
for (var i = 0; i < data.length; i++) { 
$("#dpCity").append($("<option></option>").val(data[i].Area_ID).html(data[i].Area_Name)); 
}; 
break; 
case "2": 
$("#dpArea").html(""); 
$("#dpArea").append("<option value='' selected='selected'>请选择...</option>"); 
for (var i = 0; i < data.length; i++) { 
$("#dpArea").append($("<option></option>").val(data[i].Area_ID).html(data[i].Area_Name)); 
}; 
break; 
default: 
break; 
} 
}); 
} 
// --></mce:script> 
</form> 
</body> 
</html> 



三、基于ExtJS 3.2的Ajax框架。 
后台ashx: 
 代码如下:

using System; 
using System.Collections.Generic; 
using System.Web; 
using Downmoon.Framework.Controllers; 
using Downmoon.Framework.Model; 
using System.Text; 
namespace dropdown_ExtJS32_Net2.Ajax 
{ 
/// <summary> 
/// Summary description for GetAreaXml 
/// </summary> 
public class GetAreaXml : IHttpHandler 
{ 
//string baseCode = "000000"; 
public void ProcessRequest(HttpContext context) 
{ 
string parentId = "000000"; 
if (context.Request["pid"] != null) 
{ 
parentId = context.Request["pid"].ToString(); 
} 
//parentId = (parentId.Length > 0) ? parentId : "000000"; 
////string parentId2 = "000000"; 
////if (context.Request["pid2"] != null) 
////{ 
//// parentId2 = context.Request["pid2"].ToString(); 
////} 
#region tony 2010.2.7 update 
List<Area> list = new List<Area>(); 
//if (parentId.Length > 0) 
//{ 
list = Factory.GetAreaController().GetAreaListFindByParentID(parentId); 
//} 
////else if (parentId2.Length > 0) 
////{ 
//// list = Factory.GetAreaController().GetAreaListFindByParentID(parentId2); 
////} 
#endregion 
context.Response.AddHeader("Cache-Control", "no-cache, must-revalidate"); 
context.Response.ContentEncoding = System.Text.Encoding.UTF8; 
context.Response.ContentType = "text/html"; 
StringBuilder sb = new StringBuilder(); 
for (int i = 0; i < list.Count; i++) 
{ 
sb.Append("{\"Area_Name\":\"" + list[i].Area_Name + "\","); 
sb.Append("\"Area_ID\":\"" + list[i].Area_ID + "\"},"); 
} 
string json = sb.ToString().TrimEnd(','); 
context.Response.Write("{\"Results\":[" + json + "]}"); 
} 
public bool IsReusable 
{ 
get 
{ 
return false; 
} 
} 
} 
} 
 
前台页面.aspx 
 代码如下:

<!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>demo a dropdownlist by extjs 3.2 </title> 
<link rel="stylesheet" href="Scripts/ext/3.2/resources/css/ext-all.css" mce_href="Scripts/ext/3.2/resources/css/ext-all.css" /> 
<mce:script type="text/javascript" src="Scripts/ext/3.2/adapter/ext/ext-base.js" mce_src="Scripts/ext/3.2/adapter/ext/ext-base.js"></mce:script> 
<mce:script type="text/javascript" src="Scripts/ext/3.2/ext-all.js" mce_src="Scripts/ext/3.2/ext-all.js"></mce:script> 
<mce:script type="text/javascript"><!-- 
Ext.onReady(function () { 
//alert("extjs is Ok!"); 
}); 
function $() { 
return Ext.get(arguments[0]); 
} 
/*Area*/ 
function GetAreas() { 
//alert($(arguments[1])); 
var cityCtrl = $(arguments[1]).child("select"); 
var cityCtrlContainer = $(arguments[1]); 
cityCtrl.dom.options.length = 0; 
if ($(arguments[0]).getValue() == "") { cityCtrlContainer.hide(); return; } 
cityCtrl.disabled = true; 
var selectValue2 = $(arguments[0]).getValue(); 
Ext.Ajax.request({ 
url: arguments[2], 
params: { pid: selectValue2 }, 
method: 'GET', 
success: function (result, request) { 
//alert(params); 
var jsonData = Ext.util.JSON.decode(result.responseText); 
//alert(jsonData.Results.length); 
if (jsonData.Results.length > 0) { 
cityCtrl.dom.options.add(new Option("请选择", "000000")); 
for (var i = 0; i < jsonData.Results.length; i++) { 
cityCtrl.dom.options.add(new Option(jsonData.Results[i].Area_Name, jsonData.Results[i].Area_ID)); 
} 
cityCtrl.disabled = false; 
cityCtrlContainer.show(); 
} 
else { 
cityCtrlContainer.hide(); 
} 
}, 
failure: function (result, request) { Ext.MessageBox.alert('Failed', 'Successfully posted form: ' + action.date); } 
}); 
} 

// --></mce:script> 
</head> 
<body> 
<form id="form1" runat="server"> 
<table width="500" border="0" cellpadding="0" cellspacing="2"> 
<tr> 
<td height="25" bgcolor="#EAEAEA"> 
<div style="float: left; height: 20px; line-height: 20px;"> 
请选择</div> 
<asp:DropDownList Style="float: left;" mce_Style="float: left;" ID="dropProvince" runat="server" /> 
<div style="float: left; height: 20px; line-height: 20px;"> 
省</div> 
<asp:Panel ID="panelArea" runat="server"> 
<asp:DropDownList Style="float: left;" mce_Style="float: left;" ID="dropArea" runat="server" /> 
<div style="float: left; height: 20px; line-height: 20px;"> 
市</div> 
</asp:Panel> 
<asp:Panel ID="panelArea2" runat="server" > 
<asp:DropDownList Style="float: left;" mce_Style="float: left;" ID="dropArea2" runat="server" /> 
<div style="float: left; height: 20px; line-height: 20px;"> 
县</div> 
</asp:Panel> 
</td> 
</tr> 
</table> 
</form> 
</body> 
</html> 

效果如图：


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