文件按二进制流下载

               //将文件保存到本机上                Response.Clear();                Response.AddHeader("Content-Disposition", "attachment; filename=" + Server.UrlEncode(filename));                Response.AddHeader("Content-Length", fi.Length.ToString());                Response.ContentType = "application/octet-stream";                Response.Filter.Close();                Response.WriteFile(fi.FullName);                Response.End();