TL;DR – would be post-mortem finalization available thanks to phantom references useful in .NET? What is your opinion, especially based on your experience with the finalization of your use cases? Please, share your insights in comments!
Both JVM and CLR has the concept of finalizers which is a way of implicit (non-deterministic) cleanup – at some point after an object is recognized as no longer reachable (and thus, may be garbage collected) we may take an action specified by the finalizer – a special, dedicated method (i.e. Finalize in C#, finalize in Java). This is mostly used for the purpose of cleaning/releasing non-managed resources held by the object to be reclaimed (like OS-limited, and thus valuable, file or socket handles).
However, such form of finalization has its caveats (elaborated in detail below). That’s why in Java 9 finalize() method (and thus, finalization in general) has been deprecated, which is nicely explained in the documentation:
“Deprecated. The finalization mechanism is inherently problematic. Finalization can lead to performance issues, deadlocks, and hangs. Errors in finalizers can lead to resource leaks; there is no way to cancel finalization if it is no longer necessary; and no order is specified among calls to finalize methods of different objects. Furthermore, there are no guarantees regarding the timing of finalization. The finalize method might be called on a finalizable object only after an indefinite delay, if at all.”