private void CtrlInvitationCard_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
 {
     if (selectedCard != null)
     {
         selectedCard.IsSelected = false;
     }
     selectedCard            = sender as InvitationCardControl;
     CtrlTestInfo.TestId     = selectedCard.Invitation.TestId;
     selectedCard.IsSelected = true;
     selectedCard.Focus();
 }
        void UpdatePage()
        {
            CtrlInvitationsWrap.Children.Clear();

            InvitationCardControl card;

            for (int i = CtrlPageNav.PageFirstElementIndex; i < CtrlPageNav.PageLastElementIndex; i++)
            {
                card = new InvitationCardControl(invitations[i]);
                card.MouseLeftButtonUp += CtrlInvitationCard_MouseLeftButtonUp;
                CtrlInvitationsWrap.Children.Add(card);
            }

            if (CtrlInvitationsWrap.Children.Count == 0)
            {
                CtrlInvitationsEmpty.Visibility = Visibility.Visible;
            }
            else
            {
                CtrlInvitationsEmpty.Visibility = Visibility.Collapsed;
            }
        }