通过文件流stream下载文件

        public ActionResult ShowLocalizedXML(int id)

        {

            string orderName = "";

            string xmlString = GetXmlStream(id,out orderName);

            ViewBag.Xml = xmlString;

            XmlDocument doc = new XmlDocument();

            doc.CreateComment(xmlString);

            byte[] array = Encoding.UTF8.GetBytes(xmlString);

           //array = UnicodeEncoding.Convert(Encoding.UTF8, Encoding.Unicode, array);

            MemoryStream stream = new MemoryStream(array);

            Response.Cache.SetCacheability(HttpCacheability.NoCache);

            Response.ContentType = "application/octet-stream";

            Response.AppendHeader("Content-Disposition", "attachment; filename="+orderName+".xml");//Filename改成什么格式，就会下载什么格式文件

            Response.AppendHeader("Content-Length", "" + stream.Length);

            byte[] bts = new byte[stream.Length];

            stream.Seek(, SeekOrigin.Begin);

            stream.Read(bts, , (int)stream.Length);

            Response.OutputStream.Write(bts, , bts.Length);

            return View();

        }