DispatcherTimerSample.cs

using System;
using System.Windows;
using System.Windows.Threading;

namespace WpfApplication1
{
    public partial class MainWindow : Window
    {
        DispatcherTimer timer = new DispatcherTimer() { Interval = TimeSpan.FromSeconds(1) };
        int sec = 5;

        public MainWindow()
        {
            InitializeComponent();
            timer.Tick += timer_Tick;
            timer.Start();
        }

        void timer_Tick(object sender, EventArgs e)
        {
            if (sec > 0)
            {
                sec--;
                timerText.Text = sec.ToString();  //timerText是介面上的一個TextBlock
            }
            else
                timer.Stop();
            
        }
    }
}