This is why in most C# paradigms developers would never implement this type of state-based class model. You'd have a user class, with all the required methods t

This is why in most C# paradigms developers would never implement this type of state-based class model. You'd have a user class, with all the required methods that guard (at runtime) against invalid states and transition mutably as required. Most C# environments (UI, web frameworks) are not designed around functional concepts, especially immutable objects/collections.