protected override async void OnNavigatedTo(NavigationEventArgs e)
        {
            base.OnNavigatedTo(e);
            _classes = await WindesheimManager.GetAllClasses();

            FillListBox();
        }
        protected override async void OnNavigatedTo(NavigationEventArgs e)
        {
            if (e.Parameter == null)
            {
                return;
            }

            _klassen = e.Parameter as IEnumerable <string>;
            if (_klassen == null)
            {
                return;
            }

            if (!_klassen.Any())
            {
                return;
            }

            EnablePinButton(_klassen);

            var requests = await Task.WhenAll(_klassen
                                              .AsParallel()
                                              .Select(async x => await WindesheimManager.GetScheduleForClass(x)));

            if (requests.Any(x => x is NoInternet))
            {
                lvSchedule.Items.Add(NO_INTERNET_AVAILBLE);
                return;
            }

            var completeSchedule = requests.Cast <Success <List <Les> > >().SelectMany(x => x.Value)
                                   .OrderBy(x => x.roosterdatum)
                                   .ThenBy(x => x.starttijd)
                                   .GroupBy(x => x.roosterdatum)
                                   .ToArray();

            foreach (var day in completeSchedule)
            {
                var date = day.Key.ToString("dddd dd MMMM", CultureInfo.CurrentCulture);
                lvSchedule.Items.Add(date);

                foreach (var lesson in day)
                {
                    lvSchedule.Items.Add(lesson);
                }
            }
        }