注：由于本人主要做后台的就只用到了IO空间下面的一些东西，贴个小小的级联效果来吧，
废话少说先拿代码说话了，
复制代码 代码如下:
Demo.show={
Test:function(e,Y)
{
config=Demo.config;
function onshengchange(e)
{
var sheng = Y.Node.get('#'+config.sheng).get("value");
var speccode = Y.Node.get('#'+config.speciality);
var years = Y.Node.get('#'+config.years);
var timeslist =Y.Node.get('#'+config.times);
var content="<option selected=selected>请选择</option>";
speccode.setContent("<option selected=selected>加载数据....</option>");
years.setContent(content);
timeslist.setContent(content);
var requestSpeciality = Y.io("Test.aspx", {
                method:"POST",
                data:"type=sheng&sheng="+sheng,
                arguments:{event:"cclchange"},
                on:
                    {
                        success:successHandler,
                        failure:failureHandler
                    }
                }
            );
}
function onspecialitychange(e)
{

var sheng = Y.Node.get('#'+config.sheng).get("value");
var speccode = Y.Node.get('#'+config.speciality).get("value");
var years = Y.Node.get('#'+config.years);
var timeslist =Y.Node.get('#'+config.times);
var content="<option selected=selected>请选择</option>";
years.setContent("<option selected=selected>加载数据....</option>");
timeslist.setContent(content);
var requestSpeciality = Y.io("Test.aspx", {
                method:"POST",
                data:"type=speciality&cclid="+ccl+"&speccode="+speccode,
                arguments:{event:"specchange"},
                on:
                    {
                        success:successHandler,
                        failure:failureHandler
                    }
                }
            );
}
function onyearchange(e)
{
var sheng = Y.Node.get('#'+config.sheng).get("value");
var speccode = Y.Node.get('#'+config.speciality).get("value");
var year = Y.Node.get('#'+config.years).get("value");
var timeslist =Y.Node.get('#'+config.times);
timeslist.setContent("<option selected=selected>加载数据....</option>");
var requestSpeciality = Y.io("Test.aspx", {
                method:"POST",
                data:"type=year&sheng="+sheng+"&speccode="+speccode+"&year="+year,
                arguments:{event:"yearchange"},
                on:
                    {
                        success:successHandler,
                        failure:failureHandler
                    }
                }
            );
}

function ontimeslistchagne(e){
//这里可以一直连下去
}
function successHandler(id, o,args){
if(args!=null)
if(args.event!=null)
{
if(args.event=='shengchange')
{
var root = o.responseXML.documentElement;
var speciality =Y.Node.get('#'+config.speciality);
var content="<option selected=selected>请选择</option>";
             for(i=0;i<root.childNodes.length;i++)
             {
             var node=root.childNodes[i];
             var value=node.getElementsByTagName("Code")[0].text;
             var text=node.getElementsByTagName("CName")[0].text;
             content+="<option value="+value +">"+text+"</option>";
             }
             speciality.setContent(content);
}
else if(args.event=='specchange')
{
var root = o.responseXML.documentElement;
var yearlist =Y.Node.get('#'+config.years);
var content="<option selected=selected>请选择</option>";
             for(i=0;i<root.childNodes.length;i++)
             {            
             var value=root.childNodes[i].text;
             var text=value;
             content+="<option value="+value +">"+text+"</option>";
             }
             yearlist.setContent(content);
}
else if(args.event=='yearchange')
{
var root = o.responseXML.documentElement;
var timeslist =Y.Node.get('#'+config.times);
var content="<option selected=selected>请选择</option>";
var times=Y.DataType.Number.parse(root.text);
if(times==null)
times=0;
             for(i=0;i<times;i++)
             {            
             content+="<option value="+(i+1) +">"+(i+1)+"</option>";
             }
             timeslist.setContent(content);
}

            }
        }

        
        function failureHandler(id, o){
        alert("数据获取成功");
        }
        var sheng = Y.Node.get('#'+config.sheng);
var speccode = Y.get('#'+config.speciality);
var year = Y.get('#'+config.years);
var timeslist =Y.Node.get('#'+config.times);

        sheng.on("change",oncclchange);
        speccode.on("change",onspecialitychange);
        year.on("change",onyearchange);
        timeslist.on("change",ontimeslistchagne);

}
};
YUI().use("node","datatype-number","io-base",function(Y) {
function onload(e)
{
Demo.show.Test(e,Y);
}
Y.on("load", onload, window);
});


复制代码 代码如下:
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Test.aspx.cs" Inherits="Test" %>
<!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>无标题页</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:DropDownList ID="sheng" runat="server">
</asp:DropDownList>
<asp:DropDownList ID="speciality" runat="server">
</asp:DropDownList>
<asp:DropDownList ID="year" runat="server">
</asp:DropDownList>
<asp:DropDownList ID="times" runat="server">
</asp:DropDownList>
</div>
</form>
</body>
</html>


复制代码 代码如下:
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
public partial class Test : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.ClientScript.IsClientScriptIncludeRegistered("YUI"))
Page.ClientScript.RegisterClientScriptInclude("YUI", path + "/build/yui/yui-min.js");
if (!Page.ClientScript.IsClientScriptIncludeRegistered("CLINET"))
Page.ClientScript.RegisterClientScriptInclude("CLINET", path + "/js/clinet.js");
StringBuilder scriptBlock = new StringBuilder();
scriptBlock.Append("<script type="text/javascript"><!--
");
scriptBlock.Append("Demo.config={");
scriptBlock.Append("sheng:'" + this.sheng.ClientID + "',");
scriptBlock.Append("speciality:'" + this.specialityList.ClientID + "',");
scriptBlock.Append("years:'" + this.yearList.ClientID + "',");
scriptBlock.Append("times:'" + this.timesList.ClientID + "'");
scriptBlock.Append("};");
scriptBlock.Append("
// --></script>");
Page.ClientScript.RegisterClientScriptBlock(GetType(), "QualityAssessmentPlanCascadingDropDown", scriptBlock.ToString());

}
}

这上面为主要代码，上面那段JS我实际写的请求的是一个WEBService ，你可以换一个aspx页面都行，

还有一些后台处理的到数据的就没有贴出来了，每一个级联请求的后台都是返回一个对象数组 ，具体的解释就不用说了， 不懂的在讨论。。。