private void NewTicketClick(object sender, System.Windows.RoutedEventArgs e)
        {
            if (_viewModel.SelectedEvent == null)
            {
                _viewModel.ShowDialog("You must select an event in order to add ticket reservations");
                return;
            }

            if (_viewModel.SelectedEvent.AvailableTickets == 0)
            {
                _viewModel.ShowDialog("This event has no available tickets");
                return;
            }

            var dialog = new EditTicketReservation(0, _viewModel.SelectedEvent);
            dialog.Show();
        }
        private void OnEdit()
        {
            var selected = SelectedTicket;

            if ( selected == null )
            {
                ShowDialog( "You must select a ticket in order to edit a ticket" );
                return;
            }

            var id = selected.ID;
            var dialog = new EditTicketReservation( id, SelectedEvent );
            dialog.Show();
        }