中文文件名下载在火狐乱码

我们一般下载中文文件名一般会utf-8编码再下载，火狐浏览器会出现文件名乱码，解决办法，火狐浏览器文件名不编码，直接下载：

   httpcontext curcontext = httpcontext.current;

            // 设置编码和附件格式
            curcontext.response.contenttype = "application/vnd.ms-excel";
            curcontext.response.contentencoding = encoding.utf8;
            curcontext.response.charset = "";
            strfilename = strfilename + datetime.now.tostring("yyyymmddhhmmss");

            string useragent = curcontext.request.servervariables["http_user_agent"].tolower();
            if (useragent.indexof("firefox", stringcomparison.ordinal) == -1) 
            {
                strfilename = httputility.urlencode(strfilename, encoding.utf8) + ".xls";
            }
            curcontext.response.appendheader("content-disposition",
                "attachment;filename=" + strfilename);

            curcontext.response.binarywrite(listtoexcel(list, strfilename, titledic).getbuffer());
            curcontext.response.end();