protected CollectionViewSourceBase([NotNull] UICollectionView collectionView,
string itemTemplate = AttachedMemberConstants.ItemTemplate)
{
Should.NotBeNull(collectionView, "collectionView");
_selectedItems = new HashSet <object>();
_collectionView = collectionView;
_itemTemplateMember = BindingServiceProvider
.MemberProvider
.GetBindingMember(collectionView.GetType(), itemTemplate, false, false);
}