Hi

I'm implementing a coupon system for my TC solution.
On the client side I have a input field for each orderline where I can input a coupon code. When validating the coupons, I call TeaCommerce.updateOrderLineProperty from the client with a 'couponCode' property, and on the server I hook into WebshopEvents.OrderLinePropertiesUpdated to check for a valid coupon code.
If the coupon is not valid for that orderline, I need to signal that to the client. The only way I can find to do this is but setting 'couponCode' property on the passed in orderlineproperties and call order.save().
On the client I then check for OderLinePropertiesUpdated[0].Value for empty and display a message accordingly.

This approach only work the first time. I the customer types it wrongly, I can notify them, but on the second call to TeaCommerce.updateOrderLineProperty I'm not able to set the property to empty on the server and the client gets the entered value back, and hence it's valid. I've  notised a difference between then first and the following calls: The ID of the property that gets returnered the client is different from 0 on the first call, but allways 0 on the following calls.

I run Umbraco 4.7.0 and TC 1.4.1.2

The serverside code is:

void WebshopEvents_OrderLinePropertiesUpdated(Order order, OrderLine orderLine, IEnumerable<OrderLineProperty> orderLineProperties)
{
    var discount = orderLineProperties.Where(p => p.Alias == "couponCode")
  .FirstOrDefault();
    if (discount != null)
    {
        if (orderLine.IsValidCoupon(discount.Value))
        {
            var coupon = DocumentLibrary.GetCoupon(discount.Value);
            orderLine.UnitPriceWithoutVAT = 
        orderLine.OriginalUnitPriceWithoutVAT * (1-coupon.Discount/100);
            order.Save();
        }
        else
        {
            discount.Value = "";
            order.Save();
        }
    }
}

1. Is this a TeaCommece error?
2. Is there a better way to signal the client?

Kind regards

Bo