Orc.FilterBuilder.ConditionTreeItem.OnConditionItemsCollectionChanged C# (CSharp) Method

        private void OnConditionItemsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            if (e.OldItems != null)
            {
                foreach (var item in e.OldItems)
                {
                    var conditionTreeItem = (ConditionTreeItem)item;

                    if (ReferenceEquals(conditionTreeItem, this))
                    {
                        conditionTreeItem.Parent = null;
                    }

                    conditionTreeItem.Updated -= OnConditionUpdated;
                }
            }

            var newCollection = (e.Action == NotifyCollectionChangedAction.Reset) ? (IList)sender : e.NewItems;
            if (newCollection != null)
            {
                foreach (var item in newCollection)
                {
                    var conditionTreeItem = (ConditionTreeItem)item;

                    conditionTreeItem.Parent = this;
                    conditionTreeItem.Updated += OnConditionUpdated;
                }
            }
        }