BaconographyWP8.Common.ReorderListBox.UpdateDropTarget C# (CSharp) Method

        private void UpdateDropTarget(double dragItemOffset, bool showTransition)
        {
            Point dragPoint = ReorderListBox.GetHostCoordinates(
                new Point(this.dragInterceptorRect.Left, this.dragInterceptorRect.Top + dragItemOffset));
            IEnumerable<UIElement> targetElements = VisualTreeHelper.FindElementsInHostCoordinates(dragPoint, this.itemsPanel);
            ReorderListBoxItem targetItem = targetElements.OfType<ReorderListBoxItem>().FirstOrDefault();
            if (targetItem != null)
            {
                GeneralTransform targetTransform = targetItem.DragHandle.TransformToVisual(this.dragInterceptor);
                Rect targetRect = targetTransform.TransformBounds(new Rect(new Point(0, 0), targetItem.DragHandle.RenderSize));
                double targetCenter = (targetRect.Top + targetRect.Bottom) / 2;

                int targetIndex = this.itemsPanel.Children.IndexOf(targetItem);
                int childrenCount = this.itemsPanel.Children.Count;
                bool after = dragItemOffset > targetCenter;

                ReorderListBoxItem indicatorItem = null;
                if (!after && targetIndex > 0)
                {
                    ReorderListBoxItem previousItem = (ReorderListBoxItem)this.itemsPanel.Children[targetIndex - 1];
                    if (previousItem.Tag as string == ReorderListBoxItem.DropAfterIndicatorState)
                    {
                        indicatorItem = previousItem;
                    }
                }
                else if (after && targetIndex < childrenCount - 1)
                {
                    ReorderListBoxItem nextItem = (ReorderListBoxItem)this.itemsPanel.Children[targetIndex + 1];
                    if (nextItem.Tag as string == ReorderListBoxItem.DropBeforeIndicatorState)
                    {
                        indicatorItem = nextItem;
                    }
                }
                if (indicatorItem == null)
                {
                    targetItem.DropIndicatorHeight = this.dragIndicator.Height;
                    string dropIndicatorState = after ?
                        ReorderListBoxItem.DropAfterIndicatorState : ReorderListBoxItem.DropBeforeIndicatorState;
                    VisualStateManager.GoToState(targetItem, dropIndicatorState, showTransition);
                    targetItem.Tag = dropIndicatorState;
                    indicatorItem = targetItem;
                }

                for (int i = targetIndex - 5; i <= targetIndex + 5; i++)
                {
                    if (i >= 0 && i < childrenCount)
                    {
                        ReorderListBoxItem nearbyItem = (ReorderListBoxItem)this.itemsPanel.Children[i];
                        if (nearbyItem != indicatorItem)
                        {
                            VisualStateManager.GoToState(nearbyItem, ReorderListBoxItem.NoDropIndicatorState, showTransition);
                            nearbyItem.Tag = ReorderListBoxItem.NoDropIndicatorState;
                        }
                    }
                }

                this.UpdateDropTargetIndex(targetItem, after);
            }
        }