C# 中IRecipient的具体使用

public interface IRecipient<TMessage>
    where TMessage : class
{
    void Receive(TMessage message);
}

public interface IMessenger
{
    void Register<TRecipient, TMessage>(TRecipient recipient)
        where TRecipient : class, IRecipient<TMessage>
        where TMessage : class;
    
    void Send<TMessage>(TMessage message)
        where TMessage : class;
    
    void Unregister<TMessage>(object recipient)
        where TMessage : class;
}

public class WeakReferenceMessenger : IMessenger
{
    // 实现细节...
}

public class UserLoggedInMessage
{
    public string Username { get; }
    
    public UserLoggedInMessage(string username)
    {
        Username = username;
    }
}

public class UserDashboardViewModel : IRecipient<UserLoggedInMessage>
{
    public void Receive(UserLoggedInMessage message)
    {
        // 处理用户登录消息
        Console.WriteLine($"欢迎, {message.Username}!");
    }
    
    public UserDashboardViewModel(IMessenger messenger)
    {
        // 注册接收消息
        messenger.Register<UserLoggedInMessage>(this);
    }
}

var messenger = new WeakReferenceMessenger();
var dashboardVM = new UserDashboardViewModel(messenger);

// 发送消息
messenger.Send(new UserLoggedInMessage("张三"));

public class MultiMessageReceiver : 
    IRecipient<UserLoggedInMessage>,
    IRecipient<UserLoggedOutMessage>
{
    public void Receive(UserLoggedInMessage message)
    {
        // 处理登录
    }
    
    public void Receive(UserLoggedOutMessage message)
    {
        // 处理登出
    }
    
    public MultiMessageReceiver(IMessenger messenger)
    {
        messenger.Register<UserLoggedInMessage>(this);
        messenger.Register<UserLoggedOutMessage>(this);
    }
}

public void Receive(UserLoggedInMessage message)
{
    if (message.Username == "admin")
    {
        // 特殊处理管理员登录
    }
}

public void Dispose()
{
    _messenger.Unregister<UserLoggedInMessage>(this);
    _messenger.Unregister<UserLoggedOutMessage>(this);
}

// 在发送方 ViewModel
_messenger.Send(new DataUpdatedMessage(updatedData));

// 在接收方 ViewModel
public class DataConsumerViewModel : IRecipient<DataUpdatedMessage>
{
    public void Receive(DataUpdatedMessage message)
    {
        // 更新数据
    }
}

// 在 View 的代码隐藏中
public partial class MainView : Window, IRecipient<NavigateMessage>
{
    public MainView()
    {
        InitializeComponent();
        var messenger = App.Current.Services.GetService<IMessenger>();
        messenger.Register<NavigateMessage>(this);
    }
    
    public void Receive(NavigateMessage message)
    {
        // 处理导航请求
        frame.Navigate(message.TargetPage);
    }
}