static void Main(string[] args)
        {
            FileStream fs = new FileStream("1.rar", FileMode.Open);
            BinaryReader dr = new BinaryReader(fs);
            byte [] bs=new byte[(int)fs.Length ];
            dr.Read(bs,0,bs.Length);
            dr.Close();
                                                 
            HttpListener listen = new HttpListener();
            Console.WriteLine("The Connect sucessed ");
            listen.Prefixes.Add("http://127.0.0.1:80/My/1.rar/");
            listen.Start();
      while(true)
      { 
            HttpListenerContext context = listen.GetContext();
            context.Response.AddHeader("Content-disposition", "attachment:filename='1.rar'");
            context.Response.AppendHeader("Content-Lengh", bs.Length.ToString());
            context.Response.AddHeader("Content-Transfer-Encoding", "binary");
            context.Response.ContentType = "Application/octet-stream";
            try
            {
                
                    Console.WriteLine("Sending...........");
                    context.Response.OutputStream.Write(bs, 0, bs.Length);
                    context.Response.OutputStream.Flush();
                    context.Response.OutputStream.Close();

             }
            catch (Exception e)
             {

                 Console.WriteLine(e.Message.ToString());
                 Console.ReadLine();

             }
            
        }
//这段代码执行时，在浏览器地址栏里输入：http://127.0.0.1/My/1.rar
//迅雷能检测到文件的大小，也能实现下载。但是抛出异常：
//在前缀“http://127.0.0.1:80/My/1.rar/”上侦听失败，因为它与计算机上的现有注册冲突。

//有时还不稳定，不能实现下载。

//望各位指教一二，如果有更好的代码能实现如上的下载方法，望赐教。