asp.net下载文件实现代码

//打开要下载的文件 System.IO.FileStream r = new System.IO.FileStream(FileName, System.IO.FileMode.Open); //设置基本信息              Response.Buffer = false;              Response.AddHeader("Connection", "Keep-Alive");              Response.ContentType = "application/octet-stream";              Response.AddHeader("Content-Disposition", "attachment;filename=" + System.IO.Path.GetFileName(FileName));              Response.AddHeader("Content-Length", r.Length.ToString());                           while (true)              {                  //开辟缓冲区空间                  byte[] buffer = new byte[1024];                  //读取文件的数据                  int leng = r.Read(buffer, 0, 1024);                  if (leng == 0)//到文件尾，结束                      break;                  if (leng == 1024)//读出的文件数据长度等于缓冲区长度，直接将缓冲区数据写入                      Response.BinaryWrite(buffer);                  else                  {                      //读出文件数据比缓冲区小，重新定义缓冲区大小，只用于读取文件的最后一个数据块                      byte[] b = new byte[leng];                      for (int i = 0; i < leng; i++)                              b[i] = buffer[i];                      Response.BinaryWrite(b);                  }              }              r.Close();//关闭下载文件              Response.End();//结束文件下载 该方法有下载提示框，服务器端可以知道何时下载完毕。