public void LoadMainCategories() { MainCategories = new NotifyTaskCompletion <ObservableCollection <MainCategory> >(_mainCategoriesRepository.GetCollectionAsync().ContinueWith(tsk => { var collection = new ObservableCollection <MainCategory>(tsk.Result); collection.Insert(0, new MainCategory() { ID = 0, Name = "Alle hoofdcategorieen" }); return(collection); } )); MainCategoriesForEdit = new NotifyTaskCompletion <ObservableCollection <MainCategory> >(_mainCategoriesRepository.GetCollectionAsync().ContinueWith(tsk => { var collection = new ObservableCollection <MainCategory>(tsk.Result); return(collection); } )); }