wpf计时器

wpf应用程序间隔一段时间触发一个事件，代码如下：

       public MainWindow()
        {
            InitializeComponent();
            DispatcherTimer timer = new DispatcherTimer();
            timer.Interval = TimeSpan.FromMilliseconds();
            timer.Tick += MyEventHandler;
            timer.Start();
        }

        public void MyEventHandler(object sender, EventArgs e)
        {

            tbxTime.Text = DateTime.Now.ToString("yyyy/MM/dd HH:m:ss");
        }