private void InitializeCommands()
 {
     /// Komeda transferu z prawego listboxa do lewego
     MoveToLeftCommand = new RelayCommand(button =>
     {
         if (RightSelectedItem != null)
         {
             LeftItemsList.Add(RightSelectedItem);
             LeftSelectedItem = RightSelectedItem;
             RightItemsList.Remove(RightSelectedItem);
             RightSelectedItem = null;
         }
     });
     /// Komenda transferu z lewego do prawego listboxa
     MoveToRightCommand = new RelayCommand(button =>
     {
         if (LeftSelectedItem != null)
         {
             RightItemsList.Add(LeftSelectedItem);
             RightSelectedItem = LeftSelectedItem;
             LeftItemsList.Remove(LeftSelectedItem);
             LeftSelectedItem = null;
         }
     });
 }
        // Refresh list - czyści listy a tymczasowa lista temp -> dodaje przedmioty do prawej listy
        public void RefreshList()
        {
            var temporaryList = new List <Item> {
                new Item {
                    ItemName = "Banan", ItemPrice = 1.25
                }, new Item()
                {
                    ItemName = "Ananas", ItemPrice = 5.88
                }, new Item {
                    ItemName = "kokos", ItemPrice = 10
                }, new Item {
                    ItemName = "Kawa", ItemPrice = 15.50
                }, new Item {
                    ItemName = "Orzechy", ItemPrice = 7.23
                }, new Item {
                    ItemName = "Kiełbasa", ItemPrice = 6.50
                }, new Item {
                    ItemName = "Ananas", ItemPrice = 6.43
                }, new Item {
                    ItemName = "Napój energetyczny", ItemPrice = 4.30
                },
            };

            LeftItemsList.Clear();
            RightItemsList.Clear();

            temporaryList.ForEach(item => LeftItemsList.Add(item));
        }