Question

I understand the hierarchy between the two and know how to convert between them, but is there anything fundamentally wrong with declaring a list like this?

IEnumerable<int> _bookmarkedDeals = new List<int>();

I don’t need to change the list at any point, its either created or recreated as a whole.

As an alternative, possibly this

IEnumerable<int> _bookmarkedDeals = Enumerable.Empty<int>();

Answer 1

Well, in this case, _bookmarkedDeals will be empty so the declaration is somewhat useless. That being said, nothing wrong with treating a List as an IEnumerable.