Hi...

It looks like there's something fishy going on with orders during the checkout flow in the starter kit (1.2.0.0).

I am doing a dynamic calculation of shipping cost and other calculations to orders during the checkout (e.g. discount handling). Under specific circumstances, Tea Commerce adds new entries in the Order table, causing the current order to change.

The problem is easy to recreate:

1. Create an event handler using the code below
2. Open the starter kit webshop, add an item to the basket and go through the checkout flow - stop at the "Accept" page. Notice that the shipping cost for the order is shown as the value calculated by the UpdateShippingFee() method in the event handler.
3. Access the database from SQL Management Studio and execute "SELECT TOP 10 o.Id, o.ManipulatedShippingFeeWithoutVAT, o.CreatedDate FROM TeaCommerce_Order o ORDER BY o.Id DESC". Note the Id of the order (the first result). Also notice that the colunm ManipulatedShippingFeeWithoutVAT has the correct value set by the UpdateShippingFee() method in the event handler.
4. In the webshop, flip backwards through the checkout flow until you reach "Customer information" (Click "< Back to Shipping and Payment", then "< Back to Customer information")
5. Change country for the order.
6. In SQL Management Studio, refresh the query. For some reason what looks like a copy of the order has been added to the Order table. Why that happens is beyond me, but at least it does contain a correct, updated value in the ManipulatedShippingFeeWithoutVAT column - so far so good.
7. In the webshop, go to the next step in the checkout flow (click "Shipping and Payment >")
8. In SQL Management Studio, refresh the query. Yet another order has been added to the Order table - this time with a NULL value in the ManipulatedShippingFeeWithoutVAT column.
9. In the webshop, go to the next step in the checkout flow (click "Next >")
10. As one might expect, the shipping cost for the order is now listed as the default shipping price for the chosen provider.

I'm not entirely certain why Tea Commerce would create a copy of the order in step 5. It might be a feature, it might be a bug - I don't know. 

The order copy created in step 7 seems most definitively to be a bug. It happens when the OriginalUnitPriceWithoutVAT property on the orderlines is read by the GetOriginalPriceWithoutVAT() method in the event handler. Read - not written to. Comment out the line and the order is not copied in step 7. And what's even more weird; if you attach a debugger, you'll see that the GetOriginalPriceWithoutVAT() method is not even invoked in step 7!

Any ideas?

~Kenn

    public class TestEventHandler : ITeaCommerceExtension {
        public void Initialize() {
            WebshopEvents.OrderLineChanged += WebshopEvents_OrderLineChanged;
            WebshopEvents.ShippingMethodChanged += WebshopEvents_ShippingMethodChanged;
            WebshopEvents.CountryChanged += WebshopEvents_CountryChanged;
        }

        private bool UpdateShippingFee(Order order) {
            // get the shipping fee per country per currency (simplified...)
            var shippingFees = new Dictionary<string, Dictionary<string, decimal>> {
                         {"dk", new Dictionary<string, decimal> {{"dkk", 10.00m}, {"eur", 1.33m}, {"usd", 1.80m}}},
                         {"de", new Dictionary<string, decimal> {{"dkk", 20.00m}, {"eur", 2.66m}, {"usd", 3.60m}}},
                         {"us", new Dictionary<string, decimal> {{"dkk", 50.00m}, {"eur", 6.65m}, {"usd", 9.00m}}}
            };
            var fee = shippingFees[order.Country.CountryCode.ToLowerInvariant()][order.CurrencyISOCode.ToLowerInvariant()];

            // update the shipping fee as applicable
            if(order.ShippingFee == fee) {
                return false;
            }
            order.ShippingFee = fee;
            return true;
        }

        private decimal GetOriginalPriceWithoutVAT(Order order) {
            // this code also triggers the error... but the code below is better for showing where the error occurs :-)
            //return order.OrderLines.Sum(o => o.OriginalUnitPriceWithoutVAT);

            // sum the total price without VAT
            var total = 0m;
            foreach(var item in order.OrderLines) {
                // access the OriginalUnitPriceWithoutVAT property to trigger the error
                // (the original code uses OriginalUnitPriceWithoutVAT for something else, this code is just for triggering the error)
                total += item.OriginalUnitPriceWithoutVAT;

                // accessing other properties instead - e.g. Quantity - does not seem to trigger the error
                //total += item.Quantity;
            }
            return total;
        }

        private void WebshopEvents_OrderLineChanged(Order order, OrderLine orderLine) {
            // trigger the error
            // note: the code does not change anything in the order, and we don't even call order.Save() - but still the error occurs
            var priceWithoutVAT = GetOriginalPriceWithoutVAT(order);
        }

        private void WebshopEvents_CountryChanged(Order order, Country country) {
            if(UpdateShippingFee(order)) {
                order.Save();
            }
        }

        private void WebshopEvents_ShippingMethodChanged(Order order, ShippingMethod shippingMethod) {
            if(UpdateShippingFee(order)) {
                order.Save();
            }
        }
    }