I would like to prevent users from saving class instances to the database. To do so, I've tried combinations of mapping the class as immutable and using a read-only cache. All tests result in preventing UPDATE and DELETE operations, but not INSERT.

I could map a non-nullable column as read only (update="false" insert="false"), but the exception returned to the user is misleading. Furthermore, the solution is not bulletproof since someone can change the database schema.

Is there a clean way to specify such behavior in nHibernate? Ideally, I would like to specify an attribute at the class level, but haven't found such an attribute in the documentation.

At which level are you working ?

The dumb answer would be "don't give to your users the UI to do Insert/Update/Delete" :arrow:

If you are at a lower level (like providing an interface to UI developers) then:
1- They should be aware that this entities are "immutable"
2- You can throw exception when trying to Save/Update/Delete an immutable entity :D

But if you still want NHibernate to manage that for you, then catch the "exception returned to the user that is misleading" and throw another...

Perhaps,you try it In your entity class those read_only property have a getter and not setter.

Thanks for the advice, KPixel. I ended up implementing this policy for the time being and it works well.

Looks interesting! I'll give it a try. Thanks!