Is the enumeration order of the Stack<T> collection well defined?

Hi! I used the [`Stack`](https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.stack-1) collection recently to implement an algorithm, whose correctness now depends on the `Stack` having a LIFO enumeration order. I checked the documentation to see if this enumeration order is well defined, but I can't find an explicit statement about this. I found though an [old StackOverflow question](https://stackoverflow.com/questions/37725449/stack-and-queue-enumeration-order "Stack and Queue enumeration order"), where [the accepted answer](https://stackoverflow.com/a/37725773/11178549) (by Matthew Watson) includes this excerpt:

> **The Stack.GetEnumerator() *strongly implies* that LIFO order is used.**
>
> If you look at [the example for `Stack.GetEnumerator()` in Microsoft's documentation](https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.stack-1.getenumerator) and inspect the stated output, you can see that it is in LIFO order.
>
> This strongly suggests that Microsoft fully intend a Stack to be enumerated in LIFO order - but they forgot (or didn't bother to) to explicitly document this!

I would like to ask if the current LIFO behavior is just an implementation detail, or if it's a publicly documented guarantee on which algorithms can rely on.

Thanks!

Inizia dalla documentazione dell’API di Stack e dal relativo esempio di GetEnumerator(), quindi confronta la formulazione con l’output LIFO segnalato e la discussione collegata su StackOverflow. L’issue è completata quando la documentazione indica chiaramente, in seguito a una decisione dei maintainer, se l’ordine di enumerazione è una garanzia supportata.

Scritto dal modello di indicizzazione a partire dal testo della issue.