I want to get all pages with type of ArticlePage from a controller of a partial. 

Currently I have this code and pages is null?

[ChildActionOnly]
        public ActionResult Navigation()
        {
            var model = new NavigationPartialViewModel();

            var pageTypeId = ServiceLocator.Current.GetInstance<ContentTypeRepository>()
                .Load<ArticlePage>()
                .ID
                .ToString();


            var criterias = new PropertyCriteriaCollection
            {
                new PropertyCriteria()
                {
                    Condition = CompareCondition.Equal,
                    Name = "PageTypeID",
                    Type = PropertyDataType.PageType,
                    Value = pageTypeId,
                    Required = true
                }
            };

            var repository = ServiceLocator.Current.GetInstance<IPageCriteriaQueryService>();

            var pages = repository.FindPagesWithCriteria(
                PageReference.StartPage,
                criterias);

            return PartialView(model);
        }