public void Changer(object sender, SelectionChangedEventArgs e) { WpfDrinkzy.CustomerServiceRef.Customer c = (WpfDrinkzy.CustomerServiceRef.Customer)CustomerList.SelectedItem; StorageList.ItemsSource = null; List <WpfDrinkzy.StorageServiceRef.Storage> allProducts = new List <WpfDrinkzy.StorageServiceRef.Storage>(); allProducts.AddRange(sClient.GetAllDrinkStorage(c.ID).ToList()); allProducts.AddRange(sClient.GetAllAlchoholStorage(c.ID).ToList()); allProducts.AddRange(sClient.GetAllHelflaskStorage(c.ID).ToList()); StorageList.ItemsSource = allProducts; }