添加文件然后自动打开

               //这里的案例是自动生成excel
                string pathstr = System.Web.HttpContext.Current.Server.MapPath("/FilePath");
                if (!System.IO.Directory.Exists(pathstr))
                    System.IO.Directory.CreateDirectory(pathstr);

                string filePath = Server.MapPath("/FilePath/" + filename);
                FileStream file = new FileStream(filePath, FileMode.Create);
                xssfworkbook.Write(file);
                file.Close();
                //重点
                System.Diagnostics.Process.Start(filePath);