文件流的方式下载文件

//流方式下载
  protected void Button4_Click(object sender, EventArgs e)
  {
  string fileName = "aaa.zip";//客户端保存的文件名
  string filePath = Server.MapPath("DownLoad/aaa.zip");//路径

  //以字符流的形式下载文件
  FileStream fs = new FileStream(filePath, FileMode.Open);
  byte[] bytes = new byte[(int)fs.Length];
  fs.Read(bytes, 0, bytes.Length);
  fs.Close();
  Response.ContentType = "application/octet-stream";
  //通知浏览器下载文件而不是打开
  Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
  Response.BinaryWrite(bytes);
  Response.Flush();
  Response.End();

  }