public static void DownFileStream(MemoryStream ms, string fileName)

        {

            if (ms !=Stream.Null)

            {

                if (HttpContext.Current.Request.UserAgent != null && HttpContext.Current.Request.UserAgent.ToUpper().IndexOf("FIREFOX", StringComparison.Ordinal) != -)

                {

                    fileName = "=?UTF-8?B?" + Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(fileName)) + "?=";

                }

                else

                {

                    fileName = System.Web.HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8);

                    if (fileName != null) fileName = fileName.Replace("+", "%20");

                }

                HttpContext.Current.Response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}.xls",fileName));

                HttpContext.Current.Response.AddHeader("Content-Length", ms.Length.ToString());

                HttpContext.Current.Response.AddHeader("Content-Transfer-Encoding", "binary");

                HttpContext.Current.Response.ContentType = "application/octet-stream;charset=utf-8";

                HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF8;

                HttpContext.Current.Response.BinaryWrite(ms.ToArray());

                ms.Close();

                ms.Dispose();

            }

        }