关于.NET实现断点续传问题

Question

平台：VS 2005,IIS 5.1 ,WINDOWS XP，.NET 2.0
问题：不能实现断点续传
关键代码如下：
 HttpWebRequest hwr = (HttpWebRequest)HttpWebRequest.Create(url);//url为一个服务器的文件路径
 FileStream fs = new FileStream(local, FileMode.OpenOrCreate);//local为本地一个未下载完成的文件

 if (fs.Length> 0)
          hwr.AddRange(fs.Length);//添加Range，告诉服务器把文件名为url的文件从fs.Length处开始发送数据到客户端

 int bufferSize = 512;//缓冲区大小为512字节
 byte[] buffer = new byte[bufferSize];
 Stream s = hwr.GetResponse().GetResponseStream();//开始获取服务器端数据
 int readSize = s.Read(buffer, 0, bufferSize);
  while (readSize > 0)
  {

         fs.Write(buffer, 0, readSize);
         readSize = s.Read(buffer, 0, bufferSize);
  }

无论何时执行这段代码，服务器总是从文件开始的地方返回数据，并不是要求的从fs.Length出开始返回

Answer 1

/// </summary>   
        /// <param name="URL">服务器URL地址</param>   
        /// <param name="Filename">存放到本地的路径</param>   
        /// <param name="Prog">进度条</param>   
        public static void DownFile(string URL, string Filename, ProgressBar Prog)   
        {   
  
            try  
            {   
                HttpWebRequest Myrq = (HttpWebRequest)HttpWebRequest.Create(URL);   
  
  
                HttpWebResponse myrp = (HttpWebResponse)Myrq.GetResponse();   
                long totalBytes = myrp.ContentLength;   
                Prog.Maximum = (int)totalBytes;   
                Stream st = myrp.GetResponseStream();   
                Stream so = new FileStream(Filename, FileMode.Create);   
                long totalDownloadedByte = 0;   
                byte[] by = new byte[1024];   
                int osize = st.Read(by, 0, (int)by.Length);   
                while (osize > 0)   
                {   
                    totalDownloadedByte = osize + totalDownloadedByte;   
                    Application.DoEvents();   
                    so.Write(by, 0, osize);   
                    Prog.Value = (int)totalDownloadedByte;   
                    osize = st.Read(by, 0, (int)by.Length);   
                }   
                so.Close();   
                st.Close();   
                MessageBox.Show("下载完毕!", "下载提示：", MessageBoxButtons.OK, MessageBoxIcon.Asterisk, MessageBoxDefaultButton.Button1);   
            }   
  
            catch (Exception ex)   
            {   
                MessageBox.Show(ex.Message, "提示", MessageBoxButtons.OK, MessageBoxIcon.Asterisk,   
                    MessageBoxDefaultButton.Button1);   
            }   
  
  

参照这里
http://blog.csdn.net/hxy2261/archive/2009/08/25/4482026.aspx

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努力+方法=成功

Answer 2

断点续传，你需要使用Range HTTP头。每次发送已经下载的字节数

request.AddRange((int)lStartPos); //设置Range值

代码搜索

c# 断点 下载 range

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