点击下载按钮下载文件到本地 download stream to local

 protected void Down_Load(object sender, EventArgs e)
 {
        //create a stream for the file
        Stream stream = null;
        //this controls how many bytes to read at a time and send to the client
        int bytesToRead = 10000;
        //buffer to read bytes in chunk size specified above
        byte[] buffer = new byte[bytesToRead];
        string url = "http://stv1.222.net/mv/dkp10608.mp4";
        string fileName = "11.mp4";
        try
        {
            //create a webrequest to get the file
            HttpWebRequest fileReq = (HttpWebRequest)WebRequest.Create(url);
            HttpWebResponse fileResp = (HttpWebResponse)fileReq.GetResponse();
            if (fileReq.ContentLength > 0)
                fileResp.ContentLength = fileReq.ContentLength;
            stream = fileResp.GetResponseStream();
            var resp = HttpContext.Current.Response;
            resp.ContentType = "application/octet-stream";
            //indicate the type of data being sent
            resp.AddHeader("Content-Disposition", "attachment;filename=\"" + fileName + "\"");
            resp.AddHeader("Content-Length", fileResp.ContentLength.ToString());

            int length;
            do
            {
                //verify that client is connected
                if (resp.IsClientConnected)
                {
                    //read data into the buffer
                    length = stream.Read(buffer, 0, bytesToRead);
                    //and write it out to the response‘s output stream
                    resp.OutputStream.Write(buffer, 0, length);
                    //flush the data
                    resp.Flush();
                    //clear the data
                    buffer = new byte[bytesToRead];
                }
                else
                {
                    //cancel the download if client has disconnected
                    length = -1;
                }
            } while (length > 0); //repeat until no data is read
        }
        catch (Exception)
        {
            throw;
        }
        finally
        {
            if (stream != null)
            {
                //close the input stream
                stream.Close();
            }
        }
}