我是用ASP.NET 2.0 开发的，使用母版页和内容页，在进入A页面时，我在里面写了javascript超链接到B页面，同时把值返回给A页面

当到页面到本页时
  using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Text;
using System.Text.RegularExpressions;
using System.Data.SqlClient;
using PetShop.SQLServerDAL;
using PetShop.DBUtility;public partial class ShoppingCart : System.Web.UI.Page
{
    public static ArrayList al = new ArrayList();
    private ArrayList resstr = null;
    protected System.Web.UI.HtmlControls.HtmlInputHidden hidden_text;     protected void Page_PreInit(object sender, EventArgs e)
    {
        string type = Request.QueryString["type"];
        string itemId = Request.QueryString["addItem"];
        string prodid = Request.QueryString["prodid"];
        string sizestr = Request.QueryString["sizestr"];
        string strcolor_s = Request.QueryString["color"];
        Session["oldvalue"] = -1;
        Session["prodid"] = prodid;
        Session["itemId"] = itemId;
        string scriptstr = "";
        StringBuilder sb2 = new StringBuilder();
        if (!IsPostBack) 
        {
            if (type == "2")
            {
                if (!string.IsNullOrEmpty(itemId))
                {
                    string[] str_split = null;
                    if (sizestr != "")
                    {
                        if (sizestr != "" && sizestr != null)
                        {
//sizestr返回的值是color=58&size=L,M所以在这里截取出单个的尺寸，再进行插入。
                            str_split = Regex.Split(sizestr, ",", RegexOptions.IgnoreCase);
                        }
                        if (str_split.Length > 0)
                        {
                            //循环截取的字符串。
                            for (int ss = 0; ss < str_split.Length; ss++)
                            {
                                string str_sizerange = str_split[ss].ToString();
                                string products = prodid + strcolor_s + str_sizerange;
                                string str_query_item = "select itemId from item where prodid+prodcolor+prodsize = '" + products.Trim() + "'";
//执行查询语句。
                                SqlDataReader dr = SqlHelper.ExecuteReader_s(SqlHelper.ConnectionStringLocalTransaction, CommandType.Text, str_query_item);
                                //Session["_products"] = products;
                                while (dr.Read())
                                {
                                    if (products != "" && products != null)
                                    {
                                      //******************************************
                                      // 将重新组合的值写到Label中这段代码有错误
                                       // if (Session["_products"] != null)
                                           // Label1.Text = Session["_products"].ToString();
                                      //*********************************************
                                        //document.getElementById('父窗口中的对象').value = '';
                                    }
                                }
                            }
                        }
                    }
                }//结束!string.IsNullOrEmpty(itemId)
                
                Response.Redirect("~/ShoppingCart.aspx",true);
            }//结束if (type == "2")zhan
            else if (type == "1")  
            {
                if (itemId != "" && itemId != null)
                {
                    
                    string str_query_item = "select prodColor from item where itemId = '" + itemId + "'";
                    SqlDataReader dr = SqlHelper.ExecuteReader_s(SqlHelper.ConnectionStringLocalTransaction, CommandType.Text, str_query_item);
                    if (dr.Read())
                    {
                        string str_getcolor = dr["prodColor"].ToString();
                        if (str_getcolor != "")
                        {
                            StringBuilder sb = new StringBuilder();
                            if (!IsClientScriptBlockRegistered("clientScript"))
                            {
                                sb.Append("<script language='javascript'>\n");
                                sb.Append("var wink2 ;");
//得到返回过来的值
                                sb.Append("var wink = window.showModalDialog( 'ChooseSize.aspx?id=" + itemId + "&prodid=" + prodid + "','','dialogWidth:400px;dialogHeight:300px;center:yes;'); ");
                                sb.Append("wink2 = wink;");
                                sb.Append("alert(wink2);");
                                sb.Append("if (wink != '') { ");
//重新超链接到本页
                                sb.Append("window.location.href = 'ShoppingCart.aspx?type=2&addItem=" + itemId + "&prodid=" + prodid + "&sizestr='+wink2;\n");
                                sb.Append(" };");
                                sb.Append("</script>");
                                RegisterClientScriptBlock("clientScript", sb.ToString());
                            }
                        }
                        else
                        {
                            //没有颜色时尺寸也不应该有，将此产品直接加入购物车
                            Profile.ShoppingCart.Add(itemId.Trim());
                            Profile.Save();
                            Response.Redirect("~/ShoppingCart.aspx", true);
                        }
                    }
                }
            }
        }
    }
请大侠指点
    }