MVVMLight的简单使用

1.MVVM模式

前台：

<StackPanel>
    <TextBox Margin="10" Height="20" Background="LightCyan" x:Name="text1"/>
    <TextBox Margin="10,0" Height="20" Background="LightCyan" Text="{Binding Title}"/>
    <Button Content="Button" Margin="10"  Command="{Binding AddCommand}" CommandParameter="{Binding ElementName=text1,Path=Text}"/>
</StackPanel>

后台：

class MainWindowViewModel:ViewModelBase
{
    private string title;
    public string Title
    {
        get { return title; }
        set{
            title = value;
            this.RaisePropertyChanged();
        }
    }
    
    //带参数
    public RelayCommand<string> AddCommand { get; set; }

    public MainWindowViewModel()
    {
        AddCommand = new RelayCommand <string>(Show);
    }
    
    private void Show(string str)
    {
        Title = str;
    }
}

2.Messager消息传递

它是一种轻量级、简单易用的消息传递机制，可以有效地解耦 ViewModel 和 View 的依赖关系，从而提高代码的可维护性和可测试性。

/// <summary>
/// 注册订阅事件  （在 View 或 ViewModel 中注册对特定消息的处理方法）
/// </summary>
/// <typeparam name="TMessage">传参类型</typeparam>
/// <param name="recipient">订阅实例</param>
/// <param name="token">发送与接收定义的key值</param>
/// <param name="action">订阅事件触发的action</param>
/// <param name="keepTargetAlive">持续控制实例存在，防止被回收清除</param>
public void Register<TMessage>(object recipient, object token, Action<TMessage> action, bool keepTargetAlive = false);
 
/// <summary>
/// 注销订阅事件  （取消在 View 或 ViewModel中对特定消息的处理方法的注册）
/// </summary>
/// <typeparam name="TMessage">传参类型</typeparam>
/// <param name="recipient">订阅实例</param>
/// <param name="token">发送与接收定义的key值</param>
void Unregister<TMessage>(object recipient, object token);
 
/// <summary>
/// 被订阅方触发事件  （在 ViewModel中发送消息，将消息发送给已经注册了该消息的所有接收器）
/// </summary>
/// <typeparam name="TMessage">传参类型</typeparam>
/// <param name="message">参数数据</param>
/// <param name="token">key</param>
public void Send<TMessage>(TMessage message, object token);

注册消息：

public MainWindow()
{
    // InitializeComponent call is required to merge the UI
    // that is defined in markup with this class, including  
    // setting properties and registering event handlers           
    InitializeComponent();
    this.DataContext = new MainWindowViewModel();
    Messenger.Default.Register<string>(this,"token1",(info)=> { MessageBox.Show(info); });
}

发送消息：

private void Show(string str)
{
    Title=str;
    Messenger.Default.Send<string>("hello", "token1");
}

注销消息：

Messenger.Default.Unregister<string>(this, "token1");