<Window x:Class="HelloWorld.TimeShowerWindow"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

        xmlns:local="clr-namespace:HelloWorld"

        mc:Ignorable="d"

        Title="WPF Timer" Height="350" Width="525">

    <Window.Resources>

        <Style TargetType="{x:Type Button}">

            <Setter Property="Padding" Value="5" />

            <Setter Property="Margin" Value="5" />

        </Style>

    </Window.Resources>

    <Grid>

        <Grid.RowDefinitions>

            <RowDefinition Height="Auto" />

            <RowDefinition Height="*" />

        </Grid.RowDefinitions>

        <StackPanel Orientation="Horizontal">

            <Button x:Name="startDispatcher" Content="Start Dispatcher Timer" Click="StartDispatcher" />

            <Button x:Name="startTimer" Content="Start Timer" Click="StartTimer" />

            <Button x:Name="reset" Content="Reset" IsEnabled="False" Click="Reset" />

        </StackPanel>

        <Label x:Name="clock"

               Grid.Row="1"

               VerticalAlignment="Center"

               HorizontalAlignment="Center"

               FontSize="25"

               FontWeight="Bold" />

    </Grid>

</Window>

using System;

using System.ComponentModel;

using System.Threading;

using System.Windows;

using System.Windows.Threading;

namespace HelloWorld

{

    /// <summary>

    /// TimeShowerWindow.xaml 的交互逻辑

    /// </summary>

    public partial class TimeShowerWindow : Window

    {

        private DispatcherTimer dispatcherTimer; //方式1（推荐WPF开发时使用）

        private Timer timer;  //方式2：通用方式

        public TimeShowerWindow()

        {

            InitializeComponent();

            // 方式1 - 对象初始化，以及指定相应的委托程序

            dispatcherTimer = new DispatcherTimer { Interval = new TimeSpan(, , ) };

            dispatcherTimer.Tick += OnDispatcherTimer;

            // 方式2 - 对象初始化，以及指定相应的委托程序

            timer = new Timer(OnTimer, null, Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);

        }

        /// <summary>

        /// 方式1 的按钮点击事件处理

        /// </summary>

        /// <param name="sender"></param>

        /// <param name="e"></param>

        private void StartDispatcher(object sender, RoutedEventArgs e)

        {

            dispatcherTimer.Start();

            ShowTime();

            EnableStartButtons(false);

        }

        /// <summary>

        /// 方式2 的按钮点击事件处理

        /// </summary>

        /// <param name="sender"></param>

        /// <param name="e"></param>

        private void StartTimer(object sender, RoutedEventArgs e)

        {

            timer.Change(TimeSpan.Zero, new TimeSpan(, , ));

            EnableStartButtons(false);

        }

        /// <summary>

        /// 重置按钮的点击事件处理

        /// </summary>

        /// <param name="sender"></param>

        /// <param name="e"></param>

        private void Reset(object sender, RoutedEventArgs e)

        {

            timer.Change(Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);

            dispatcherTimer.Stop();

            EnableStartButtons(true);

            clock.Content = string.Empty;

        }

        /// <summary>

        /// 启用或禁用按钮

        /// </summary>

        /// <param name="enabled"></param>

        private void EnableStartButtons(bool enabled)

        {

            startDispatcher.IsEnabled = enabled;

            startTimer.IsEnabled = enabled;

            reset.IsEnabled = !enabled;

        }

        private void OnDispatcherTimer(object sender, EventArgs e)

        {

            ShowTime();

        }

        private void OnTimer(object state)

        {

            //子线程中更新 UI 线程，必须使用

            Dispatcher.Invoke(() => ShowTime());

        }

        /// <summary>

        /// 此方法运行在 UI 线程

        /// </summary>

        private void ShowTime()

        {

            clock.Content = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");

        }

    }

}