delegate long myDel(int first, int second);

        FileStream fs;

        byte[] _byte;

        protected void Page_Load(object sender, EventArgs e)

        {

            Response.ContentType = "image/jpeg";

            fs = new FileStream(Server.MapPath("~/file/") + HttpUtility.UrlDecode("你好.jpg"), FileMode.Open);

            _byte = new byte[fs.Length];

            IAsyncResult ir = fs.BeginRead(_byte, , (int)fs.Length, null, null);

            fs.Read(_byte, , fs.EndRead(ir));

            fs.Close();

            Response.BinaryWrite(_byte);

        }

        protected void Button1_Click(object sender, EventArgs e)

        {

            string filePath = Server.MapPath("~/file/") + HttpUtility.UrlDecode("你好.jpg");

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

            Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode("你好.jpg", Encoding.UTF8));

            //FileInfo fi = new FileInfo(filePath);

            //Response.WriteFile(fi.FullName);

            //Response.End();

            int length = ;

            byte[] arr = new byte[ *  * ];

            using (FileStream fs = new FileStream(filePath, FileMode.Open))

            {

                length = fs.Read(arr, , arr.Length);

            }

            byte[] arrNew = new byte[length];

            System.Buffer.BlockCopy(arr, , arrNew, , length);

            Response.BinaryWrite(arrNew);

        }

        public static void ResponseFile(string filePath, HttpContext context, bool hasfileName)

        {

            Stream iStream = null;

            byte[] buffer = new Byte[];

            int length;

            long dataToRead;

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

            context.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(Path.GetFileName(filePath), Encoding.UTF8));

            using (iStream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read))

            {

                dataToRead = iStream.Length;

                while (dataToRead > )

                {

                    if (context.Response.IsClientConnected)

                    {

                        length = iStream.Read(buffer, , );

                        context.Response.OutputStream.Write(buffer, , length);

                        context.Response.Flush();

                        buffer = new Byte[];

                        dataToRead = dataToRead - length;

                    }

                    else

                    {

                        dataToRead = -;

                    }

                }

            }