<Window x:Class="demo.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        Title="MainWindow" Height="300" Width="300">    <StackPanel Margin="5">        <TextBox Name="txt">Text in a text box.</TextBox>        <Button Click="cmdBreakRules_Click">Break the rules</Button>        <Button Click="cmdFollowRules_Click">Follow the rules</Button>    </StackPanel></Window>

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Windows;using System.Windows.Controls;using System.Windows.Data;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Imaging;using System.Windows.Navigation;using System.Windows.Shapes;using System.Threading;using System.Windows.Threading;namespace demo{    /// <summary>    /// MainWindow.xaml 的交互逻辑    /// </summary>    public partial class MainWindow : Window    {        public MainWindow()        {            InitializeComponent();        }        private void UpdateTextWrong()        {            Thread.Sleep(TimeSpan.FromSeconds(3));            txt.Text = "Here is some new text.";        }        private void cmdFollowRules_Click(object sender, RoutedEventArgs e)        {            Thread thread=new Thread(UpdateTextRight);            thread.Start();        }        private void UpdateTextRight()        {            Thread.Sleep(TimeSpan.FromSeconds(3));            this.Dispatcher.BeginInvoke(DispatcherPriority.Normal, (ThreadStart)delegate()            {                UpdateTextWrong();            });            //this.Dispatcher.BeginInvoke(DispatcherPriority.Normal, (ThreadStart)delegate()            //{            //    //Thread.Sleep(TimeSpan.FromSeconds(3));耗时代码不能写在这里；这里用的是匿名委托            //    txt.Text = "Here is some new text.";            //});        }        private void cmdBreakRules_Click(object sender, RoutedEventArgs e)        {            Thread thread = new Thread(UpdateTextWrong);            thread.Start();        }    }}