菜鸟仍然求助【购物车问题】苦苦的改了一天都没成色

前台
<%@ 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>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                <asp:DataList ID="DataList1" runat="server" RepeatColumns="4">
                    <ItemTemplate>
                        <asp:Image ID="Image1" runat="server" ImageUrl='<%# Eval("Url") %>' 
                            Height="100px" Width="100px" />
                        <br />
                        <asp:Label ID="CnameLabel" runat="server" Text='<%# Eval("Cname") %>' />
                        <br />
                        <asp:Label ID="MoneyLabel" runat="server" Text='<%# Eval("Money") %>' />
                        <br />
                        <asp:CheckBox ID="CheckBox1" runat="server" Text="加入购物车" OnCheckedChanged="CheckBox1_CheckChanged" />
                        <br />
                        
                        <asp:Label ID="Label1" runat="server" Text='<%# Eval("ID") %>' Visible="false"></asp:Label>
                        <br />
                        
                    </ItemTemplate>
                </asp:DataList>
                <br />
                
                <asp:GridView ID="GridView1" runat="server">
                </asp:GridView>
                <br />
                <br />
                
                <br />
                <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
                <br />
                <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="提交" />
                <asp:Button ID="Button2" runat="server" onclick="Button2_Click" Text="Button" />
                <br />
                <br />
                <br />
            </ContentTemplate>
        </asp:UpdatePanel>
    
    </div>
    </form>
</body>
</html>
后台
using System;
using System.Collections;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
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;
using System.Xml.Linq;public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        
        
    }    protected void Button1_Click(object sender, EventArgs e)
    {
        ConnectionStringSettings conn = ConfigurationManager.ConnectionStrings["Strconnection"];   //给DataList数据源,从而显示产品。
        SqlConnection con = new SqlConnection(conn.ConnectionString);
        con.Open();
        SqlDataReader sdr;
        sdr = new SqlCommand("select * from Lv_sctable", con).ExecuteReader();
        DataList1.DataSource = sdr;
        DataList1.DataBind();
    }
   
    protected void Button2_Click(object sender, EventArgs e)
    {
        for (int i = 0; i < this.DataList1.Controls.Count; i++)  //遍历DataList模板中的每一个控件
        {
            if ((((CheckBox)this.DataList1.Items[i].FindControl("CheckBox1")).Checked) == true)//判断CheckBox复选框的状态是否被单击
            {
                string id = (((Label)this.DataList1.Items[i].FindControl("Label1")).Text).ToString().Trim();   //将被单击的商品的ID传送给变量id
                if (Session["sp"] == null)
                {
                   
                    Hashtable ht = new Hashtable();
                    ht.Add(id, 1);
                    Session["sp"] = ht;
                    
                }
                else
                {
                    Hashtable ht = (Hashtable)Session["sp"];
                    if (ht[id] == null)
                    {
                        ht[id] = 1;
                    }
                    else
                    {
                        ht[id] = (int)ht[id] + 1;
                    }
                    Session["sp"] = ht;
                }
                Response.Redirect("Default2.aspx");
                
            }
        }
     }
}    
我主要想问的问题就一个。 我现在多选后只能显示多选中第一次单击的那个物品信息。后面的根本没记录。我想做出一次性查询的购物车。求大神耐心教导。