<Window x:Class="SQRC_ViewModel觖发修改ViewModel属性.MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
          xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
 
         Title="{Binding Title}" Height="350" Width="525">
     <Grid>
         <Border Name="brInkMessage" Grid.Column="1" Grid.Row="2">
             <StackPanel>
                 <TextBox x:Name="txt3" Text="{Binding IsLogin, UpdateSourceTrigger=PropertyChanged}" />
                 <i:Interaction.Triggers>
                     <ei:DataTrigger Binding="{Binding IsLogin}" Value="True">
                         <ei:ChangePropertyAction TargetObject="{Binding}" PropertyName="Title"  Value="Changed" />
                     </ei:DataTrigger>
                 </i:Interaction.Triggers>
             </StackPanel>
         </Border>
     </Grid>
 </Window>

using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 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;
 
 namespace SQRC_ViewModel觖发修改ViewModel属性
 {
     /// <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 title;
         /// <summary>
         /// ??
         /// </summary>
         public string Title
         {
             get { return title; }
             set
             {
                 title = value;
                 this.RaisePropertyChanged("Title");
             }
         }
 
         private bool isLogin;
         /// <summary>
         /// ??
         /// </summary>
         public bool IsLogin
         {
             get { return isLogin; }
             set
             {
                 isLogin = value;
                 this.RaisePropertyChanged("IsLogin");
             }
         }
     }
 
     class NotificationObject : INotifyPropertyChanged
     {
         public event PropertyChangedEventHandler PropertyChanged;
 
         public void RaisePropertyChanged(string propertyName)
         {
             if (this.PropertyChanged != null)
             {
                 this.PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
             }
         }
     }
 }