Is it any harder than this? class Team { List<Player> players = new List<Player>(); public void AddPlayer(Player player) { // r

Is it any harder than this? class Team { List<Player> players = new List<Player>(); public void AddPlayer(Player player) { // rule checks here players.add(player); } public IEnumerable<Player> Players { get { return players; } } } Covers SOLID, DDD, the lot. One should never inherit the list. Encapsulate perhaps but the list is there as a fundamental structure and to inherit from it would break the encapsulation of the domain model you are constructing and increase efferent coupling.