Getting a "Value does not fall within the expected range" error when music stops playing

In my UWP App I have a ListView with all songs displayed in the Music Library folder. When you click on a song it will play it and move to the next song when the first one stops. All this works great, however when the last song plays and reaches the end I get this error

System.ArgumentException
HResult=0x80070057
Message=Value does not fall within the expected range.
Source=Windows
StackTrace:
at Windows.UI.Xaml.Controls.Primitives.Selector.put_SelectedIndex(Int32 value)

This is the code I have:

private async void objMediaPlayer_MediaEnded(object sender, RoutedEventArgs e)
    {
        mediaElement.Stop();

        if (AudioFilesLV.SelectedIndex <= AudioFilesLV.Items.Count)
        {
            AudioFilesLV.SelectedIndex = AudioFilesLV.SelectedIndex += 1;
            var file = await KnownFolders.MusicLibrary.GetFileAsync(AudioFilesLV.SelectedItem.ToString());
            if (file != null)
            {
                var stream = await file.OpenReadAsync();
                mediaElement.SetSource(stream, file.ContentType);
                mediaElement.Play();
            }
        }

        else
        {
            mediaElement.Stop();
        }
    }

    private void mediaItemList_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {

    }

    private void objMediaPlayer_MediaOpened(object sender, RoutedEventArgs e)
    {
        mediaElement.Play();
    }

The App crashes at this line:

 AudioFilesLV.SelectedIndex = AudioFilesLV.SelectedIndex += 1;

I can't figure out what the problem is. I think it is looking for the next song but there isn't one. So I need to tell the app to stop after the last song plays, but don't know how to do this?

Thanks

EDIT

private async void objMediaPlayer_MediaEnded(object sender, RoutedEventArgs e)
    {
        int LastPlayedIndex;
        LastPlayedIndex = AudioFilesLV.SelectedIndex;
            AudioFilesLV.SelectedIndex = AudioFilesLV.SelectedIndex = 1;
            var file = await KnownFolders.MusicLibrary.GetFileAsync(AudioFilesLV.SelectedItem.ToString());
            if (AudioFilesLV.SelectedIndex < AudioFilesLV.Items.Count && AudioFilesLV.SelectedIndex != LastPlayedIndex)
            {
                var stream = await file.OpenReadAsync();
                mediaElement.SetSource(stream, file.ContentType);
                mediaElement.Play();
            }

        else
        {
            mediaElement.Stop();
        }
    }

Looks like AudioFilesLV.SelectedIndex += 1 is more than AudioFilesLV.Items.Count ? Condition above is "<=", so index may be out of range. Maybe needeed another check, if .SelectedIndex is last in list, and do not increment value in this case?