private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            var fballer = Archiving.ReadFootballerFromFile(ArchivingFile);

            if (fballer != null)
            {
                foreach (var f in fballer)
                {
                    listBoxFootballer.Items.Add(f);
                }
            }
        }
        //metoda wykonana po załadowaniu okna
        //ładujemy zawartość pliku z zapisanymi piłkarzami jeśli tylko istnieje
        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            var players = Archiving.ReadPlayersFromFile(plikArchiwizacji);

            if (players != null)
            {
                foreach (var p in players)
                {
                    listBoxPlayers.Items.Add(p);
                }
            }
        }
        private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            int n = listBoxFootballer.Items.Count;

            Footballer[] fballer = null;
            if (n > 0)
            {
                fballer = new Footballer[n];
                int index = 0;
                foreach (var o in listBoxFootballer.Items)
                {
                    fballer[index++] = o as Footballer;
                }
                Archiving.SaveFootballerToFile(ArchivingFile, fballer);
            }
        }
        //nadpisujemy plik archiwum przy zamknięciu okna
        private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            int n = listBoxPlayers.Items.Count;

            Player[] players = null;
            if (n > 0)
            {
                players = new Player[n];
                int index = 0;
                foreach (var o in listBoxPlayers.Items)
                {
                    players[index++] = o as Player;
                }
                Archiving.ArchivePlayers(plikArchiwizacji, players);
            }
        }