private void BookOpened(Task <EpubBook> task) { EpubBook epubBook = task.Result; Navigation = new ObservableCollection <NavigationItemViewModel>(bookModel.GetNavigation(epubBook)); ReadingOrder = new ObservableCollection <HtmlContentFileViewModel>(bookModel.GetReadingOrder(epubBook)); if (ReadingOrder.Any()) { CurrentHtmlContentFile = ReadingOrder.First(); if (ReadingOrder.Count > 1) { nextHtmlContentFile = ReadingOrder[1]; } } IsLoading = false; NotifyPropertyChanged(nameof(IsPreviousButtonVisible)); NotifyPropertyChanged(nameof(IsNextButtonVisible)); }