public double zhk = 1;
    List<Product> pros = new List<Product>();
    protected void Page_Load(object sender, EventArgs e)
    {
            string vastr = Request["vastr"].ToString();
            List<Product> prosd = new List<Product>();
            if (vastr != "")
            {
                string[] ids = vastr.Split(',');
                for (int i = 0; i < ids.Length; i++)
                {
                    List<Product> pros = ProductService.GetAllProductById(ids[i].ToString());
                    if (pros.Count > 0)
                    {
                        Product pro = pros[0];
                        prosd.Add(pro);
                    }
                }
                ExportGridToExcel(prosd, "upxia.xls");
            }
            else
            {
                Response.Write("<script>alert('请选择您要导出的数据！');location='prozhan.aspx'</script>");
            }
        
    }

    private void ExportGridToExcel(List<Product> pros, string filename)
    {
        // 检查是否有文件名
        if (string.IsNullOrEmpty(filename))
        {
            throw new ArgumentException("Export filename is required");
        }
        // 检查是否是excel格式
        if (!filename.EndsWith(".xls"))
        {
            filename += ".xls";
        }

        StringWriter tw = new StringWriter();
        HtmlTextWriter hw = new HtmlTextWriter(tw);
        Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
        //Response.Clear();
        //Response.ContentType = "application/vnd.ms-excel";
        Response.AddHeader("content-disposition", "attachment;filename=" + filename);
        //Response.Charset = string.Empty;
        //Page.EnableViewState = false;
        //grid.RenderControl(hw);
        writeEc ec = new writeEc();
        hw.Write(ec.getEXCEL(pros, zhk));
        Response.Write(tw.ToString());
        Response.End();
    }