I have a one to many relationship between Order and OrderItem. Order keeps an ISet of OrderItems. I would like to create an Order object, add bunch of OrderItems to it and then persist the entire order. Problem is that as I start adding OrderItems to my Order, the collection keeps on replacing the previous item with the new one and I end up with only one item in my collection. This is because my OrderItem class implements an Equal method which checks the IDs for equality. Of course all new items that I add have an ID of 0 and they satisfy the equality condition. Is there a solution for this?

The only workaround I could think of is to persist each item in the database (thus getting a real ID) and then adding it to the Order. But this is such a pain. I cannot create simple in-memory orders with bunch of items.

You can manually create the id at object creation (works better with guids as they are guaranteed to be unique), and add a version tag to the xml file.

Therefore, it would look something like this:



and your mapping file would have the following :


Note: you need to add the version field to your table. You can also use a timestamp instead of the version...

So when persisting the object, nhibernate will see that you manually assigned the id and will instead verify the unsaved-value of either the version or timestamp.

Thanks. This is very helpful.