protected void Page_Load(object sender, EventArgs e)
        {
            string file_name = Request.QueryString["file_name"] == null ? "0" : Request.QueryString["file_name"];

            if (String.Equals(file_name, "0"))
            {
                Response.Redirect("/login.aspx");
            }
            else
            {
                DataTable dt = null;

                dt = Session["DataTableRangosStock"] as DataTable;

                GridViewExportUtil.ExportDataTableToExcel(dt, file_name);

                Session["DataTableRangosStock"] = null;
            }
        }