private void ButOK_Click(object sender, RoutedEventArgs e)
        {
            DateTime?begin = DpBegin.SelectedDate, end = DpEnd.SelectedDate;

            if (begin != null && end != null)
            {
                Vac.BeginDate = begin.Value;
                Vac.EndDate   = end.Value;
            }
            Vac.UpdateVacation(ConnStr);

            var wnd = this.Parent as Window;

            wnd.Close();
        }