private void CreateSalePaymentButton_Click(object sender, RoutedEventArgs e)
        {
            // Jeppe
            ISale selectedSale = saleListBox.SelectedItem as ISale;

            if (selectedSale != null)
            {
                CreatePaymentWindow dialog = new CreatePaymentWindow("sale", selectedSale);
                dialog.ShowDialog();
                saleMemberListBox.ItemsSource = ControllerFacade.RetrieveActivityMembers("sale", selectedSale);
                saleMemberListBox.Items.Refresh();
            }
            else
            {
                MessageBox.Show("Du skal vælge et produkt, før du kan oprette en betaling!");
            }
        }
        private void CreateTeamPaymentButton_Click(object sender, RoutedEventArgs e)
        {
            // Jeppe
            ITeam selectedTeam = teamListBox.SelectedItem as ITeam;

            if (selectedTeam != null)
            {
                CreatePaymentWindow dialog = new CreatePaymentWindow("team", selectedTeam);
                dialog.ShowDialog();
                teamMemberListBox.ItemsSource = ControllerFacade.RetrieveActivityMembers("team", selectedTeam);
                teamMemberListBox.Items.Refresh();
            }
            else
            {
                MessageBox.Show("Du skal vælge et hold, før du kan oprette en betaling!");
            }
        }
        private void CreateEventPaymentButton_Click(object sender, RoutedEventArgs e)
        {
            // Jeppe
            IEvent selectedEvent = eventListBox.SelectedItem as IEvent;

            if (selectedEvent != null)
            {
                CreatePaymentWindow dialog = new CreatePaymentWindow("event", selectedEvent);
                dialog.ShowDialog();
                eventMemberListBox.ItemsSource = ControllerFacade.RetrieveActivityMembers("event", selectedEvent);
                eventMemberListBox.Items.Refresh();
            }
            else
            {
                MessageBox.Show("Du skal vælge en begivenhed, før du kan oprette en betaling!");
            }
        }