WPF 后台线程操作界面元素不卡UI界面线程 Dispatcher

经常要考虑的，后台的耗时操作不要卡死主界面的问题。

<StackPanel VerticalAlignment="Center">
    <Label x:Name="lblHello">欢迎你光临WPF的世界!</Label>
    <Button Name="btnThd" Click="btnThd_Click" >多线程同步调用</Button>
    <Button Name="btnAppBeginInvoke" Click="btnAppBeginInvoke_Click" >BeginInvoke 异步调用</Button>
</StackPanel>

Behind Code：

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void ModifyUI()
    {
        //// 模拟一些工作正在进行
        //Thread.Sleep(TimeSpan.FromSeconds(2));
        //lblHello.Content = "欢迎你光临WPF的世界,Dispatcher";

        // 模拟一些工作正在进行
        Thread.Sleep(TimeSpan.FromSeconds(3));
        this.Dispatcher.Invoke(DispatcherPriority.Normal, (ThreadStart)delegate ()
        {
            lblHello.Content = "欢迎你光临WPF的世界,Dispatche  同步方法 ！！";
        });
    }

    private void btnThd_Click(object sender, RoutedEventArgs e)
    {
        Thread thread = new Thread(ModifyUI);
        thread.Start();
    }

    private void btnAppBeginInvoke_Click(object sender, RoutedEventArgs e)
    {
        new Thread(() =>
        {
            Thread.Sleep(TimeSpan.FromSeconds(3));
            Application.Current.Dispatcher.BeginInvoke(DispatcherPriority.Normal,
                new Action(() =>
                {
                    //Thread.Sleep(TimeSpan.FromSeconds(3)); // 放这里还是会卡 UI 界面线程
                    this.lblHello.Content = "欢迎你光临WPF的世界,Dispatche 异步方法！！" + DateTime.Now.ToString();
                }));
        }).Start();
    }
}