public virtual void AddItem(string productName, decimal price, int quantity)
{
if (price < 0)
throw new ArgumentException("Price can't be negative");
var shopOrderItem = new ShopOrderItem { ProductName = productName, Price = price, Quantity = quantity };
this.AddItem(shopOrderItem);
}
public virtual void AddItem(ShopOrderItem shopOrderItem)
{
this.ShopOrderItems.Add(shopOrderItem);
shopOrderItem.ShopOrder = this;
}