asp.net+jQuery应用JSON实现无刷新三级联动实例

本文应用到jquery、json、asp.net结合来实现无刷新三级联动效果，使用asp.net实现二级联动、三级联动效果很简单，不过不是无刷新就不爽了，所以收集一个无刷新联动的实现例子。

三个下拉控件：
<asp:DropDownList ID="ddl1" runat="server" Width="100px" ></asp:DropDownList>
<asp:DropDownList ID="ddl2" runat="server" Width="100px" ></asp:DropDownList>
<asp:DropDownList ID="ddl3" runat="server" Width="100px" ></asp:DropDownList>
JS代码：

Code

<script src="js/jquery-1.4.2.min.js" type="text/javascript" ></script>
<script type="text/javascript">
    $(document).ready(function () {       
        GetA();
        $("#ddl1").change(function () { GetB(); });         
        $("#ddl2").change(function () { GetC(); });        
    });     
   
    function GetA()
    {
        $("#ddl1").html("");
        $("#ddl1").append("<option value='-1' selected='selected'>请选择...</option>");
        //$("select[name$=ddl1] > option:selected").remove();
        var strId = 0;
        $.getJSON("LoadClass.ashx?ddlId="   strId, function (data) {
         for (var i = 0; i < data.length; i ) {
             $("select[name$=ddl1]").append($("<option></option>").val(data[i].ID).html(data[i].Cname));
         };
         GetB();         
     });
                
    }
    function GetB()
    {
        $("#ddl2").html(""); $("#ddl3").html("");
        var strId = $("#ddl1").attr("value");      
        if (strId != 0) {
            $.getJSON("LoadClass.ashx?ddlId="   strId, function (data) {
                for (var i = 0; i < data.length; i ) {
                    $("select[name$=ddl2]").append($("<option></option>").val(data[i].ID).html(data[i].Cname));
                };
                GetC();             
            });                           
        }          
    }
    function GetC()
    {
        $("#ddl3").html("");
        var strId = $("#ddl2").attr("value");
        if (strId != 0) {
            $.getJSON("LoadClass.ashx?ddlId="   strId, function (data) {
                for (var i = 0; i < data.length; i ) {
                    $("select[name$=ddl3]").append($("<option></option>").val(data[i].ID).html(data[i].Cname));
                };                       
            });                
        }       
    }
</script>

LoadClass.ashx
Code

using System;
using System.Web;

using System.Text;
using System.Data;

public class LoadClass : IHttpHandler {
   
    public void ProcessRequest (HttpContext context) {
        // 数组   [{"ID":"275","Cname":"A1"},{"ID":"319","Cname":"A2"},{"ID":"322","Cname":"A3"}]
        int strId = Convert.ToInt32(context.Request["ddlId"]);              
        string strSQL = "select * from Class where parent_Ptr="   strId   " order by classOrder asc ";
        db d = new db();
        DataTable dt = d.getDT(strSQL);
        StringBuilder strClass = new StringBuilder();
        if (dt != null)
        {
            strClass.Append("[");
            for (int i = 0; i < dt.Rows.Count; i )
            {
                strClass.Append("{");
                strClass.Append("\"ID\":\""   dt.Rows[i]["id"].ToString()   "\",");
                strClass.Append("\"Cname\":\""   dt.Rows[i]["classCname"].ToString()   "\"");

                if (i != dt.Rows.Count - 1)
                {
                    strClass.Append("},");
                }
            }

        }
        strClass.Append("}");
        strClass.Append("]");     
        context.Response.ContentType = "application/json";
        context.Response.ContentEncoding = Encoding.UTF8;
        context.Response.Write(strClass.ToString());
        context.Response.End();
    }

    public bool IsReusable {
        get {
            return false;
        }
    }

}注意：
//后台只能获取value值，不能直接获取text，需要通过js、控件中转
//结果：275 276 277
Label1.Text = Request.Form[ddl1.UniqueID] + " "                    + Request.Form["ddl2"] + " "                    + Request.Form[ddl3.ClientID.Replace("_", "$")] ;遇到的问题：下拉框text的值通过HiddenField控件中转 <asp:HiddenField ID="HiddenField1" runat="server" />
<asp:HiddenField ID="HiddenField2" runat="server" />
<asp:HiddenField ID="HiddenField3" runat="server" />
把选中下拉框的值赋予隐藏控件中：
<script type="text/javascript">      
var Key1 = $("#ddl1>option:selected").val();
$('#HiddenField1').val(Key1);
var Key2 = $("#ddl2>option:selected").val();
$('#HiddenField2').val(Key2);
var Key3 = $("#ddl3>option:selected").val();
$('#HiddenField3').val(Key3);   
</script>
选择下拉框后 动态赋值到HiddenField 控件中的值 无法与下拉框选中的值相对应