protected void UpdateCellConstraints()
{
PrepareCellsForLayout(CollectionView.VisibleCells);
PrepareCellsForLayout(CollectionView.GetVisibleSupplementaryViews(UICollectionElementKindSectionKey.Header));
PrepareCellsForLayout(CollectionView.GetVisibleSupplementaryViews(UICollectionElementKindSectionKey.Footer));
}