//WriteFile實現下載

        protected void Button2_Click(object sender, EventArgs e)

        {

            /*         using System.IO;                  */

            string fileName = "asd.txt";//客戶端保存的文件名

            string filePath = Server.MapPath("DownLoad/aaa.txt");//路徑

            FileInfo fileInfo = new FileInfo(filePath);

            Response.Clear();

            Response.ClearContent();

            Response.ClearHeaders();

            //如果是中文名稱可能會出現亂碼的現象可以使用Server.UrlEncode(fileName)進行編碼
            Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);

            Response.AddHeader("Content-Length", fileInfo.Length.ToString());

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

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

            Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");

            Response.WriteFile(fileInfo.FullName);

            Response.Flush();

            Response.End();

        }

        //WriteFile分塊下載

        protected void Button3_Click(object sender, EventArgs e)

        {

            string fileName = "aaa.txt";//客戶端保存的文件名

            string filePath = Server.MapPath("DownLoad/aaa.txt");//路徑

            System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);

            if (fileInfo.Exists == true)

            {

                const long ChunkSize = ;//100K 每次讀取文件，只讀取100K，這樣可以緩解服務器的壓力

                byte[] buffer = new byte[ChunkSize];

                Response.Clear();

                System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);

                long dataLengthToRead = iStream.Length;//獲取下載的文件總大小

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

                Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));

                while (dataLengthToRead >  && Response.IsClientConnected)

                {

                    int lengthRead = iStream.Read(buffer, , Convert.ToInt32(ChunkSize));//讀取的大小

                    Response.OutputStream.Write(buffer, , lengthRead);

                    Response.Flush();

                    dataLengthToRead = dataLengthToRead - lengthRead;

                }

                Response.Close();

            }

        }

        //流方式下載

        protected void Button4_Click(object sender, EventArgs e)

        {

            string fileName = "aaa.txt";//客戶端保存的文件名

            string filePath = Server.MapPath("DownLoad/aaa.txt");//路徑

            //以字符流的形式下載文件

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

            byte[] bytes = new byte[(int)fs.Length];

            fs.Read(bytes, , bytes.Length);

            fs.Close();

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

            //通知瀏覽器下載文件而不是打開

            Response.AddHeader("Content-Disposition", "attachment;  filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));

            Response.BinaryWrite(bytes);

            Response.Flush();

            Response.End();

        }