在关闭wpf中的窗口时，我是否必须取消订阅事件？

Question

the tiltle says it all, in my window (not the main window) constructor i have

EventAggregator.OnUserLoggedIn += OnUserLoggedIn;
EventAggregator.OnUserLoggedOff += OnUserLoggedOff;

is there a difference between

this.Close()

and

EventAggregator.OnUserLoggedIn -= OnUserLoggedIn;
EventAggregator.OnUserLoggedOff -= OnUserLoggedOff;
this.Close()

i've read that closing the window disposes all unmanged resources, are those events considered maneged or unmanaged?

Answer 1

Those events are managed resources if anything (I'm not sure if you can call events resources though).

Yes, you should unhook event handlers from child windows (not main window as it doesn't matter) otherwise you may experience memory leaks as garbage collector won't be able to pick up those objects as still having references.

Check this blog for more info on memory leaks and event handlers:

A classic leak common to all .NET applications, and a common oversight by developers. If you create an event handler to handle events occurring in some other object then, if you don't clear the link when you've finished, an unwanted strong reference will be left behind.

Answer 2

If you are closing the main window and your application will terminate after that you don't have to worry about unhooking the handler . All memory associated with your process is available for reclaim once process terminates.

But in case you are talking about secondary window here and your process will continue to run , you should consider unhooking the events since window will always be in memory as long as EventAggregator stays in memory and resulting in memory leak in your window class. Publisher (EventAggregator) will hold on to the subscriber object (window) as long as it stays in memory . So, window object will persist with the lifetime of EventAggregator object.