Hi

I was wondering if someone could tell me the best practice / reccomendation for the following scenario


Domain


Database



How would I go about setting up the mapping file so that I can change the the Order.CategoryId without causing(or allowing) an update to the Category table? Or shuld I just be concerned with tracking the CategoryId in my Order object, and looking up the CategoryInformation as I need it?

Thanks
Joe

I think you just need to use the following:

<many-to-one name="CategoryInformation" column="CategoryID" cascade="none" />

the cascade indicates that any changes to Category will not be persisted when Order is saved.

You might also want think about replacing the Category class with a simple enum. We have been looking at doing this for simple lookup values like this. The Description text can be assigned to the enum using a custom attribute. Attributes can also be used to mark enum values to be exported into a database table for reporting purposes.

Actually, that's not what cascade="none" does. I think there are actually a lot of misunderstandings about how saving/updating works within NHibernate. If you load the Category and Order from the database in an NHibernate session any changes made to either will be persisted through to the appropriate table based on changes with the business objects. There is no need to call Save(), simply Flush() your changes. So assuming he isn't always using transient objects and then calling Save() or Update() or SaveOrUpdate() your described cascade won't really change the behavior.

That being said I have no clue why this question is even being asked. Why are you thinking the category table will be changed? If you change your order to reference a different category the appropriate order table will be updated with the categoryId of the new reference. Isn't that exactly what you want? If you didn't change the category it won't change the category table.

What issue are you currently seeing?