COMException ocurred at end of Exercise 4.

[runceel]

When selecting same date on the CalenderViewWrapper control, then following error is occurred.

I think that you need the length check before accessing AddedDates property at the SelectedDatesChanged event handler like below:

private void CalendarView_SelectedDatesChanged(CalendarView sender, CalendarViewSelectedDatesChangedEventArgs args)
{
    // Add using System.Linq;
    if (args.AddedDates.Any())
    {
        SelectedDate = args.AddedDates[0];
    }
}

[qmatteoq]

Fixed in 6781dd0