public virtual List <doGetBillingDetailOfInvoice> GetBillingDetailByKey(string contractCode, string billingOCC, Nullable <int> billingDetailNo, string c_CURRENCY_LOCAL, string c_CURRENCY_US)
        {
            BLDataEntities context = new BLDataEntities();

            return(context.GetBillingDetailByKey(contractCode, billingOCC, billingDetailNo, c_CURRENCY_LOCAL, c_CURRENCY_US).ToList());
        }