public object Add(object item)
        {
            W1Payment w1Payment = (W1Payment)item;

            using (BookMarketDbContext db = new BookMarketDbContext())
            {
                db.AddW1Payment(
                    w1Payment.WMI_MERCHANT_ID,
                    w1Payment.WMI_CURRENCY_ID, w1Payment.WMI_DESCRIPTION,
                    w1Payment.WMI_EXPIRED_DATE, w1Payment.WMI_PAYMENT_AMOUNT,
                    w1Payment.WMI_SIGNATURE);
            }
            return GetAll().w1Payments.Last();
        }