程序代码：

 private void DownLoad()
        {
            var request = WebRequest.Create("http://112.91.92.82/down_group226/M00/10/F9/d5NjWU9sgi8AAAAAAI1JBCBiFuQ1908112/%E6%9A%97%E5%8F%B7.avi?k=o3k9tkPyCjxURbqvBPTpJw&t=1332512185&u=114.240.35.97@29851728@dpdw3zsk&file=%E6%9A%97%E5%8F%B7.avi&speed=153600");
            var response = request.GetResponse();
            var strm = response.GetResponseStream();
            Thread thread = null;
            thread = new Thread
                (
                    () =>
                    {
                        long totalLength = response.ContentLength;
                        byte[] buffer = new byte[1024 * 1024];
                        long count = 0;
                        int length = strm.Read(buffer, 0, buffer.Length);
                        FileStream fsWrite = new FileStream(@"E:\aa.avi",FileMode.Create);
                        while (length != 0)
                        {
                            fsWrite.Write(buffer,0,length);
                            count += length;
                            int percentage = (int)(count * 100 / totalLength);
                            //this.progressBar1.Value = percentage;
                            //percentage.ToString()+"%"
                            length = strm.Read(buffer, 0, buffer.Length);
                        }
                        thread.Abort();
                        strm.Close();
                        fsWrite.Close();
                    }
                );
            thread.Start();
        }