在重要的地方都有提示了，相信很容易看懂。
首先在web.config添加这个接点 在<system.web>与</system.web>之间，如下：
<system.web>
<!--for Ajaxnet-->
<httpHandlers>
<add verb="POST,GET" path="ajaxpro/*.ashx" type="AjaxPro.AjaxHandlerFactory, AjaxPro.2"/>
</httpHandlers>
<!--其他设置-->
</system.web>
然后把AjaxPro.2.dll丢到bin文件夹，然后引用它就可以了。
还是发代码吧，麻烦死了下面代码是 Default.aspx.cs的
using System;using System.Data;using System.Configuration;using System.Data.OleDb;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;public partial class _Default : System.Web.UI.Page
{ 
protected void Page_Load(object sender, EventArgs e)
{ AjaxPro.Utility.RegisterTypeForAjax(typeof(_Default)); //必要的 if(!IsPostBack)BindDc();
} /**//// <summary> /// 数据库连接 /// </summary> /// <returns></returns> public OleDbConnection myConn() { string ConnStr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + System.Web.HttpContext.Current.Server.MapPath(ConfigurationManager.AppSettings["dbpath"]); OleDbConnection conn = new OleDbConnection(ConnStr); try { conn.Open(); return conn; } catch { throw; } } /**//// <summary> /// 获取下级分类 /// </summary> [AjaxPro.AjaxMethod] public DataSet getNextClass(string cid) { //因为不希望页面可以知道字段名称 所以 as txt,id as vol 如果是sql ser 可以用 = //页面获取的 列名称 必须跟这个一同样 而且区分大小写 一般都是这个地方容易疏忽了 //所以二级分类没变化 string sql = @"select cname as txt,id as vol from webclass where parentid=" + cid; try { return getDs(sql); } catch { //throw; return null; } } /**//// <summary> /// 返回一个DataSet /// </summary> /// <param name="SQL"></param> /// <returns></returns> public DataSet getDs(string SQL) { OleDbConnection conn = myConn(); DataSet Ds = new DataSet(); OleDbDataAdapter Da = new OleDbDataAdapter(SQL, conn); try { Da.Fill(Ds); return Ds; } catch { return null; //throw; } } /**//// <summary> /// //数据绑定 /// </summary> private void BindDc() { //第一个 string sql = @"select * from webclass where Parentid=0"; ddl1.DataSource = getDs(sql); ddl1.DataTextField = "cname"; ddl1.DataValueField = "id"; ddl1.DataBind(); if (ddl1.DataSource != null) ddl1.Attributes.Add("onchange", "showNext(this.options[selectedIndex].value,'ddl2');"); //可以先判断 DropDownList.SelectedItem.Value //第二个 sql = @"select * from webclass where parentid=" + ddl1.SelectedItem.Value; ddl2.DataSource = getDs(sql); ddl2.DataTextField = "cname"; ddl2.DataValueField = "id"; ddl2.DataBind(); //第三个 if (ddl2.DataSource != null) ddl2.Attributes.Add("onchange", "showNext(this.options[selectedIndex].value,'ddl3');"); sql = @"select * from webclass where parentid=" + ddl2.SelectedItem.Value; ddl3.DataSource = getDs(sql); ddl3.DataTextField = "cname"; ddl3.DataValueField = "id"; ddl3.DataBind(); }
}<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %><!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"> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>AjaxPro实现无刷新三级联动</title></head><script language="javascript" type="text/javascript"> <!-- // ACLOUD 常用JS函数 function getBid(s){ return document.getElementById(s); } function getBmc(s){ return document.getElementByName(s); } //显示分类列表 function showNext(sid,obj) { if(sid==null || sid=="" || sid.length<1)return; var slt =getBid(obj); var v = _Default.getNextClass(sid).value; // 类的名称 //alert(v); //return; if (v != null){ if(v != null && typeof(v) == "object" && v.Tables != null) { slt.length = 0; slt.options.add(new Option("请选择",0)); //加了个“请选择”主要为了触发onchange事件 if(obj=="ddl2"){ getBid("ddl3").options.length=0; getBid("ddl3").options.add(new Option("请选择",0)); } for(var i=0; i<v.Tables[0].Rows.length; i++) { var txt = v.Tables[0].Rows[i].txt; //这个地方需要注意区分大小写 var vol = v.Tables[0].Rows[i].vol; //跟dataset表的列名称要一致 slt.options.add(new Option(txt,vol)); } } } return; } --></script><body> <form id="form1" runat="server"> <div> <table width="500" border="0" align="center" cellpadding="0" cellspacing="0"> <tr> <td width="99"> </td> <td width="401"> 城市<asp:DropDownList ID="ddl1" runat="server"> </asp:DropDownList> 区域<asp:DropDownList ID="ddl2" runat="server"> </asp:DropDownList> 花园<asp:DropDownList ID="ddl3" runat="server"> </asp:DropDownList></td> </tr> <tr> <td> </td> <td> </td> </tr> <tr> <td> </td> <td> </td> </tr> </table> </div> </form></body></html>http://files.cnblogs.com/asboy/AjaxDropDownlist.rar
