listcollectionview groupingcolumns and calculating the amount and quantity

private void ListCollectionView_GroupingColumnsChanged(object sender, NotifyCollectionChangedEventArgs e)
{
    if (ListCollectionView.IsGrouping == true)
    {
        if (ListCollectionView.Groups.Count > 0)
        {
            int count = 0;
            int quantity = 0;
            for (int i = 0; i < ListCollectionView.Groups.Count; i++)
            {
                foreach (InventoryItem item in ListCollectionView.Groups[i].Items)
                {
                    count++;
                    quantity += item.Quantity;
                }
            }
            _groupQuantity = quantity;
            _groupCount = count;
            OnPropertyChanged("GroupQuantity");
            OnPropertyChanged("GroupCount");
        }
        else
        {
            _groupCount = 0;
            _groupQuantity = 0;
            OnPropertyChanged("GroupQuantity");
            OnPropertyChanged("GroupCount");
        }
    }
}