WPF 中更新界面信息

   int ii = 0;
            new Thread(new ParameterizedThreadStart((i) =>
            {
                while (true)
                {
                    Thread.Sleep(400);
                    Dispatcher.BeginInvoke(new Action(() =>
                    {
                        ii += 1;
                        btn2.Content = ii.ToString();
                    }));
                }
            })).Start();

     private async void Button_Click(object sender, RoutedEventArgs e)
        {
            ServiceAgent.RestFullServiceRequestForFileDownload(new Uri("http://files.cnblogs.com/files/LittleFeiHu/ItcastWP7Simulator20110417.rar"), new DownloadProgressEventHandler((bytes) =>
            {
                S.StudentName = bytes.ToString();
                DoEvents();
                Thread.Sleep(200);
            }));
        }
        private DispatcherOperationCallback exitFrameCallback = new DispatcherOperationCallback(ExitFrame);
        public void DoEvents()
        {
            DispatcherFrame nestedFrame = new DispatcherFrame();
            DispatcherOperation exitOperation = Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, exitFrameCallback, nestedFrame);
            Dispatcher.PushFrame(nestedFrame);
            if (exitOperation.Status != DispatcherOperationStatus.Completed)
            {
                exitOperation.Abort();
            }
        }
        private static Object ExitFrame(Object state)
        {
            DispatcherFrame frame = state as DispatcherFrame;
            frame.Continue = false;
            return null;
        }