public static BehaviorsDisposable <IEnumerable <TCollItem> > AddBehavior <TCollItem>
 (
     this IEnumerable <TCollItem> collection,
     DoForEachItemCollectionBehavior <TCollItem> behavior
 )
 {
     return(collection.AddBehaviorImpl(behavior));
 }
        private static BehaviorsDisposable <IEnumerable <TCollItem> > AddBehaviorImpl <TCollItem>
        (
            this IEnumerable <TCollItem> collection,
            Action <TCollItem> onAdd,
            Action <TCollItem> onRemove = null,
            BehaviorsDisposable <IEnumerable <TCollItem> > previousBehavior = null
        )
        {
            DoForEachItemCollectionBehavior <TCollItem> behavior =
                new DoForEachItemCollectionBehavior <TCollItem>(onAdd, onRemove);

            return(collection?.AddBehaviorImpl <TCollItem>(behavior, previousBehavior));
        }
        private static BehaviorsDisposable <IEnumerable <TCollItem> > AddBehaviorImpl <TCollItem>
        (
            this IEnumerable <TCollItem> collection,
            DoForEachItemCollectionBehavior <TCollItem> behavior,
            BehaviorsDisposable <IEnumerable <TCollItem> > previousBehavior = null
        )
        {
            if (collection == null)
            {
                return(null);
            }

            DisposableBehaviorContainer <IEnumerable <TCollItem> > behaviorContainer =
                new DisposableBehaviorContainer <IEnumerable <TCollItem> >(behavior, collection);

            BehaviorsDisposable <IEnumerable <TCollItem> > behaviorsDisposable =
                new BehaviorsDisposable <IEnumerable <TCollItem> >(behaviorContainer, previousBehavior);

            return(behaviorsDisposable);
        }