protected void btnExecute_Click(object sender, EventArgs e)
        {
            //Define a workbook to store null value initially
            Workbook workbook = null;

            string path = MapPath(".");
            path = path.Substring(0, path.LastIndexOf("\\"));

            ProductsList productsList = new ProductsList(path);

            //Create a workbook based on a class's custom method
            workbook = productsList.CreateProductsList();

            if (ddlFileVersion.SelectedItem.Value == "XLS")
            {
                ////Save file and send to client browser using selected format
                workbook.Save(HttpContext.Current.Response, "ProductList.xls", ContentDisposition.Attachment, new XlsSaveOptions(SaveFormat.Excel97To2003));
            }
            else
            {
                workbook.Save(HttpContext.Current.Response, "ProductList.xlsx", ContentDisposition.Attachment, new OoxmlSaveOptions(SaveFormat.Xlsx));
            }

            //end response to avoid unneeded html
            HttpContext.Current.Response.End();
        }