public ClassRoom(Pupil p1, Pupil p2, Pupil p3, Pupil p4) : this(p1, p2, p3) { if (p4 == null) throw new ArgumentNullException(); else _pupils.Add(p4); }
public ClassRoom(Pupil p1, Pupil p2) { if (p1 == null || p2 == null) throw new ArgumentNullException(); else { _pupils.Add(p1); _pupils.Add(p2); } }