VS05里checkboxlist用JS获取 value值

using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

using System.Collections.Generic;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        List<string[]> metadata = new List<string[]>();

        metadata.Add(new string[] { "项目前期", "505004"});
        metadata.Add(new string[] { "项目进行中", "505001" });
        metadata.Add(new string[] { "项目中期", "505003" });
        metadata.Add(new string[] { "项目后期", "505005" });
        metadata.Add(new string[] { "项目结束", "505002" });
        metadata.Add(new string[] { "项目意外中止", "505006" });

        ListItem lt;

        for (int i = 0; i < metadata.Count; i++)
        {
            lt = new ListItem(metadata[i][0], metadata[i][1]);
            lt.Attributes["text"] = metadata[i][0];
            lt.Attributes["value1"] = metadata[i][1];
            this.CheckBoxList1.Items.Add(lt);
        }
    }
}

HTML code
<%@ 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">
    <title>无标题页</title>
    <script language="javascript" type="text/javascript">
    function checkAll()
    {
        var ckelems = document.getElementById("CheckBoxList1").getElementsByTagName("input");
        var spelems = document.getElementById("CheckBoxList1").getElementsByTagName("span");
        for(var i=0;i<ckelems.length;i++)
        {
            if(ckelems[i].type=="checkbox")
            {
                if(ckelems[i].checked)
                    alert('文本是 '+spelems[i].text+' 值是 '+spelems[i].value1);
            }
        }
    }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:CheckBoxList ID="CheckBoxList1" runat="server" Height="261px" Width="301px">
        </asp:CheckBoxList>
        <input id="Button1" type="button" value="button"  onclick="checkAll()"/></div>
    </form>
</body>
</html>