// код древнючий, как минимум nameof() надо использовать. И ошибки при работе с коллекцией ловить
    public abstract class OwnedCollection<TItem, TOwner> : Collection<TItem> // or KeyedCollection<TKey, TItem>
        where TItem : class
        where TOwner : class
    {
        private readonly TOwner m_Owner;
        private readonly Func<TItem, TOwner> m_GetOwner;
        private readonly Action<TItem, TOwner> m_SetOwner;

        protected OwnedCollection(
            TOwner owner,
            Func<TItem, TOwner> getOwner,
            Action<TItem, TOwner> setOwner)
        {
            Code.NotNull(owner, "owner");
            Code.NotNull(getOwner, "getOwner");
            Code.NotNull(setOwner, "setOwner");

            this.m_Owner = owner;
            this.m_GetOwner = getOwner;
            this.m_SetOwner = setOwner;
        }

        protected override void ClearItems()
        {
            foreach (var item in Items)
            {
                m_SetOwner(item, null);
            }
            base.ClearItems();
        }

        protected override void InsertItem(int index, TItem item)
        {
            Code.AssertState(m_GetOwner(item) == null, "Item is mapped to another owner.");
            base.InsertItem(index, item);

            m_SetOwner(item, m_Owner);
        }

        protected override void RemoveItem(int index)
        {
            var item = this[index];
            base.RemoveItem(index);
            m_SetOwner(item, null);
        }

        protected override void SetItem(int index, TItem item)
        {
            Code.AssertState(m_GetOwner(item) == null, "Item is mapped to another owner.");

            m_SetOwner(this[index], null);
            base.SetItem(index, item);
            m_SetOwner(item, m_Owner);
        }
    }