SiteGetChildrenQuery.cs

[ServiceConfiguration(typeof(IContentQuery))]
public class SiteGetChildrenQuery : GetChildrenQuery
{
    private readonly LanguageSelectorFactory _languageSelectorFactory;
    public SiteGetChildrenQuery(IContentQueryHelper queryHelper, IContentRepository contentRepository, LanguageSelectorFactory languageSelectorFactory)
        : base(queryHelper, contentRepository, languageSelectorFactory) { _languageSelectorFactory = languageSelectorFactory; }

    public override int Rank => 100;

    private List<int> WhiteListedContentIds => new List<int> { 1 };
    private List<Type> WhiteListedTypes => new List<Type> { typeof(DemoHomePage), typeof(LocationListPage) };
    private List<Type> OnlyFilterTheseTypes => new List<Type> { typeof(PageData) };

    protected override IEnumerable<IContent> GetContent(ContentQueryParameters parameters)
    {
        var types = parameters.TypeIdentifiers
            .Select(typeName => TypeResolver.GetType(typeName, false))
            .Where(type => type != null);

        if (OnlyFilterTheseTypes.Any() && !OnlyFilterTheseTypes.Any(x => types.Any(type => type.IsAssignableFrom(x))))
            return base.GetContent(parameters);

        if (!ContentReference.IsNullOrEmpty(parameters.ReferenceId))
            return GetChildren(types, parameters.ReferenceId, _languageSelectorFactory.AutoDetect(true));

        if (parameters.References?.Any() != true) return Enumerable.Empty<IContent>();

        return parameters.References.SelectMany(link => GetChildren(types, link, _languageSelectorFactory.AutoDetect(true)));
    }

    private IEnumerable<IContent> GetChildren(IEnumerable<Type> types, ContentReference parentId, LanguageSelector selector)
    {
        if (types?.Any() != true) return Enumerable.Empty<IContent>();

        return types.SelectMany(type => GetChildrenByType(type, parentId, selector))
                    .Distinct()
                    .Where(content => WhiteListedContentIds.Contains(content.ContentLink.ID) ||
                                WhiteListedTypes.Any(type => content.GetOriginalType().IsAssignableFrom(type)) ||
                                FilterAccess.QueryDistinctAccessEdit(content, AccessLevel.Edit) ||
                                FilterAccess.QueryDistinctAccessEdit(content, AccessLevel.Create));
    }
}