订阅的事件在不同的模块中的棱镜

Question

在我LoginModule在一个视图模型我分派事件：

void LoginUpdate(object sender, EventArgs e) 
{ 
    _eventAggregator.GetEvent<LoginStatusEvent>().Publish(_status); 
} 

在EventModule：

public class LoginStatusEvent : PubSubEvent<LoginStatus> 
{ 
} 

然后我试图订阅它在不同的模块：

public class EventModule : IModule 
{ 
    IRegionManager _regionManager; 
    IEventAggregator _eventAggregator; 
    private SubscriptionToken subscriptionToken; 
    private bool isLoggedIn { get; set; } 

    public EventModule(IEventAggregator eventAggregator, IRegionManager regionManager) 
    { 
     _regionManager = regionManager; 
     _eventAggregator = eventAggregator; 

     LoginEventsListener(); 
    } 

    public void Initialize() 
    { 

    } 

    public void LoginEventsListener() 
    { 
     LoginStatusEvent loginStatusEvent = _eventAggregator.GetEvent<LoginStatusEvent>(); 

     if (subscriptionToken != null) 
     { 
      loginStatusEvent.Unsubscribe(subscriptionToken); 
     } 

     subscriptionToken = loginStatusEvent.Subscribe(LoginStatusEventHandler, ThreadOption.UIThread, false); 
    } 

    public void LoginStatusEventHandler(LoginStatus loginStatus) 
    { 
     Trace.WriteLine(">> Got it!!"); 

    } 

} 

但是，LoginStatusEventHandler永远不会被解雇，我也没有收到任何错误。

Answer 1

当订阅事件时，OP没有保持订阅者参考，因此在某一时刻，类没有任何参考并且由GC收集。

所以在这种情况下，它将与True标志一起使用到Subscribe方法中。

由于@Haukinger权指出：

在棱镜文档 https://github.com/PrismLibrary/Prism/blob/ef1a2266905a4aa3e7087955e9f7b5a7d71972fb/Documentation/WPF/30-ModularApplicationDevelopment.md#initializing-modules

Module instance lifetime is short-lived by default. After the Initialize method is called during the loading process, the reference to the module instance is released. If you do not establish a strong reference chain to the module instance, it will be garbage collected. This behavior may be problematic to debug if you subscribe to events that hold a weak reference to your module, because your module just "disappears" when the garbage collector runs.