在ViewModel中验证登录成功时在视图中显示MessageBox

public class LoginViewModel : INotifyPropertyChanged
{
    private bool _isLoginSuccessful;
    public bool IsLoginSuccessful
    {
        get { return _isLoginSuccessful; }
        set
        {
            _isLoginSuccessful = value;
            OnPropertyChanged(nameof(IsLoginSuccessful));
        }
    }

    // 登录验证逻辑
    public void ValidateLogin(string username, string password)
    {
        // 验证逻辑省略，假设登录成功
        IsLoginSuccessful = true;
    }

    // INotifyPropertyChanged接口实现
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

<Window x:Class="YourNamespace.YourWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:YourNamespace"
        Title="Login Window" Height="300" Width="400">
    <Window.DataContext>
        <local:LoginViewModel />
    </Window.DataContext>
    <Grid>
        <!-- 省略其他控件 -->
        <TextBlock Text="Login Successful!" Visibility="Collapsed">
            <TextBlock.Style>
                <Style TargetType="TextBlock">
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding IsLoginSuccessful}" Value="True">
                            <Setter Property="Visibility" Value="Visible" />
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </TextBlock.Style>
        </TextBlock>
    </Grid>
</Window>