private void PopUp_Opened(object sender, EventArgs e) { if (!IsDropDownOpen) { this.SetCurrentValueInternal(IsDropDownOpenProperty, BooleanBoxes.TrueBox); } if (_calendar != null) { _calendar.DisplayMode = CalendarMode.Month; _calendar.MoveFocus(new TraversalRequest(FocusNavigationDirection.First)); } OnCalendarOpened(new RoutedEventArgs()); }