|ZYCWPF| 如要在DataTrigger中去修改ViewModel的MyMessage属性 有示例代码 谢谢

Question

<Window x:Class="SRQC_DataTrigger_Property.MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         Title="MainWindow" Height="350" Width="525">
     <Grid>
         <TextBox x:Name="txt1" />
         <TextBox x:Name="txt2" />
         <TextBox x:Name="txt3" Text="{Binding MyMessage}" />
     </Grid>
 </Window>
 using System.ComponentModel;
 using System.Windows;
 
 namespace SRQC_DataTrigger_Property
 {
     /// <summary>
     /// MainWindow.xaml 的交互逻辑
     /// </summary>
     public partial class MainWindow : Window
     {
         public MainWindow()
         {
             InitializeComponent();
             this.DataContext = new MainWindowViewModel();
         }
 
         class MainWindowViewModel : NotificationObject
         {
             private string myMessage;
             /// <summary>
             /// ??
             /// </summary>
             public string MyMessage
             {
                 get { return myMessage; }
                 set
                 {
                     myMessage = value;
                     this.RaisePropertyChanged("MyMessage");
                 }
             }
         }
 
         class NotificationObject : INotifyPropertyChanged
         {
             public event PropertyChangedEventHandler PropertyChanged;
 
             public void RaisePropertyChanged(string propertyName)
             {
                 if (this.PropertyChanged != null)
                 {
                     this.PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
                 }
             }
         }
     }
 } 在XAML中写触发器，如何写当txt1.Text="ABC"和txt2.Text="123"的时候，设置MyMessage="Changed";谢谢