Ive managed to get a simple shipping by weight feature added into the starter kit and its using default weight etc but I cant seem to add the product weight into the order line because this code:

foreach (OrderLine ol in order.OrderLines)
            {
                OrderLineProperty weightProp = ol.Properties.FirstOrDefault(p => p.Alias == "productWeight");
                if (weightProp != null && !string.IsNullOrEmpty(weightProp.Value))
                {
                    totalWeightInKg += (decimal)PriceHelper.ParsePrice(weightProp.Value.ToString());
                }
                else
                {
                    totalWeightInKg += defaultWeightInKg;
                }
            }

returns null, any ideas or a small code snippet I could use to add my product weight to the order line before that is run?

Thanks in advance.