How can I use Server.MapPath() from global.asax?

引用：

using System.Web.Hosting;

            string filePathcsv = "";

            string file = "";

            string strFile = "LukfookGeovindu";

            strFile = strFile + DateTime.Now.ToString("yyyyMMddhhmmss");

            strFile = strFile + ".csv";

            //file = strFile;  [email protected]

            //file = HttpContext.Current.Server.MapPath("/ReportExcel/" + strFile); //此用法存在問題

            // Server.MapPath("/ReportExcel/" + strFile);//存在問題

            file = HostingEnvironment.MapPath("/ReportExcel/" + strFile);