private void btnHapus_click(object sender, RoutedEventArgs e)
        {
            try
            {
                int index = 0;
                for (int i = 0; i < listPilihHapus.Count; i++)
                {
                    ProsesItem cariElemenList = listItemDibeli.Where <ProsesItem>(x => x.namaBarang == arrayNamaBarang[i]).Single <ProsesItem>();
                    index = listItemDibeli.IndexOf(cariElemenList);
                    listItemDibeli.RemoveAt(index);
                }

                counter = 0;
                itemBarangTerpilih.ItemsSource = null;
                itemBarangTerpilih.ItemsSource = listItemDibeli;
                HargaBarang hargaBarang = new HargaBarang();
                HargaPajak  harga       = new HargaPajak();
                outputTotalHarga.Text = "Rp. " + hargaBarang.harga(listItemDibeli).ToString();
                outputPajak.Text      = "Rp. " + harga.harga(listItemDibeli).ToString();
                outputDibayar.Text    = "Rp. " + harga.hargaTotal().ToString();
                listPilihHapus.Clear();
            }
            catch
            {
            }
        }
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            listItemDibeli = e.Parameter as List <ProsesItem>;
            itemBarangTerpilih.ItemsSource = listItemDibeli;
            HargaBarang hargaBarang = new HargaBarang();
            HargaPajak  harga       = new HargaPajak();

            outputTotalHarga.Text = "Rp. " + hargaBarang.harga(listItemDibeli).ToString();
            outputPajak.Text      = "Rp. " + harga.harga(listItemDibeli).ToString();
            outputDibayar.Text    = "Rp. " + harga.hargaTotal().ToString();
        }