net core文件流导出文件

//文件流
           using (MemoryStream mem = new MemoryStream())
         {
          //文件名
            string FileName =;

            //数据
            var OrderList = 
            
            //写入数据
            StreamWriter sw = new StreamWriter(mem);
            foreach (var item in OrderList)
            {
                sw.WriteLine();
            }
            //释放资源 无此步内存流中无数据
            sw.Close();
            return File(mem.ToArray(),"text/xml", FileName);
        }