private void SelectionChanged(object obj)
        {
            if (obj != null)
            {
                if (obj is CheckableCardModel)
                {
                    var card = obj as CheckableCardModel;
                    if (card == null)
                    {
                        return;
                    }

                    if (!card.IsChecked && AllCards.Count(x => x.IsChecked) == this._notification.CardsCount)
                    {
                        return;
                    }

                    card.IsChecked = !card.IsChecked;
                }
            }
        }