protected override async void OnActivate()
        {
            if (string.IsNullOrEmpty(PresetFileName))
            {
                return;
            }
            maxVolume = settings.Get <int>("MaxVolume").GetOrElse(100);
            MuteVolume();
            NotifyButtons();

            fileManager.FileName = PresetFileName;
            eventAggregator.Publish(new Events.HearingTest.PitchGeneratorChanged(pitchGenerator));
            eventAggregator.Publish(new Events.HearingTest.ChannelChanged(CurrentChannel));
            eventAggregator.Publish(new Events.HearingTest.StopPlaying());
            IsPlaying = false;

            PresetItems     = new ReadOnlyTraversableList <PresetItemViewModel>((await fileManager.GetCollection <PresetItemViewModel>()).ToList());
            ProgressMaximum = PresetItems.Count;
            if (!PresetItems.Any())
            {
                return;
            }

            CurrentItem = PresetItems.Next();
            pitchGenerator.Frequency = CurrentItem.Frequency;
            CurrentFrequency         = CurrentItem.Frequency.ToString(CultureInfo.InvariantCulture);
            NotifyButtons();
        }
        protected override async void OnActivate()
        {
            if (string.IsNullOrEmpty(PresetFileName))
                return;
            maxVolume = settings.Get<int>("MaxVolume").GetOrElse(100);
            MuteVolume();
            NotifyButtons();

            fileManager.FileName = PresetFileName;
            eventAggregator.Publish(new Events.HearingTest.PitchGeneratorChanged(pitchGenerator));
            eventAggregator.Publish(new Events.HearingTest.ChannelChanged(CurrentChannel));
            eventAggregator.Publish(new Events.HearingTest.StopPlaying());
            IsPlaying = false;

            PresetItems = new ReadOnlyTraversableList<PresetItemViewModel>((await fileManager.GetCollection<PresetItemViewModel>()).ToList());
            ProgressMaximum = PresetItems.Count;
            if (!PresetItems.Any())
                return;

            CurrentItem = PresetItems.Next();
            pitchGenerator.Frequency = CurrentItem.Frequency;
            CurrentFrequency = CurrentItem.Frequency.ToString(CultureInfo.InvariantCulture);
            NotifyButtons();
        }