What are the rules for when dispose() is required?

Question

Although I have been coding for some time, I\'m really just barely into what I would call an intermediate level coder. So I understand the principle of dispose(), which is

Answer 1

The Dispose pattern can be used to clear both managed and unmanaged resources. If you have unmanaged resources in your class, according to the proper IDisposable implementation you must have both Dispose and Finalize methods.

How do I know what GC knows/doesn't?

GC knows/interested only about managed objects. GC is supposed to clear objects those don’t have any strong references. It doesn’t know about your logics. For a simple and obvious example.

Let’s say you have a MainView instance which is a lasting a long time and you create another LittleView that subscribe to an event in the MainView instance.

Then you close the LittleView and it disappears. You know that you don’t need that LittleView instance anymore. But GC doesn’t know if you still need LittleView or not as there is an active event subscription to the MainWindow.

So, GC will not bother to clear LittleView instance from memory. So, what you should do is unsubscribe the event when you close the view. Then GC knows that there are no strong references to the LittleView and it’s reachable.

The post also complicates things saying managed resources may include unmanaged resources. Wow. This is getting deeper than I initially imagined. I'm still looking to easily recognize how to know what needs to be disposed. Is it the case this is a complicated list w/ conditions and context?

That’s correct, managed objects also can have unmanaged resources. All those managed objects have their finalize method to clear umanaged resources.

Wonder why you need finalize method in addition to the Dispose?

Unmanaged resources can create the most dangerous memory leaks as such memory leaks can hold on to memory until you restart the PC. So, they are very bad.

Let’s say there is managed instance InsA with some unmanaged. InsA has implemented the Dispose method in a way to clear unmanaged resources too. But what will happen if you don’t/forget to call the Dispose method? It will never clear that unmanaged memory. That’s why Finalization has come in to the functionality. So, if you forget/don’t call the Dispose, finalization will gurantee to execute the Dispose in a way that it release unmanaged resources.