I have a a one-to-many relationship between a Policy and Order

1 1..N
[Policy]----------[Order]

When I need to persist a new Order I must determine if a Policy objects already exists for the Order (based on policy number in Order). If it does not, I must create a new Policy and add the new Order to it. Otherwise, I must add the new Order to the existing Policy. How do I efficiently prevent creating a duplicate Policy if multiple concurrent Orders are being processing. Do I need to put a transaction around the entire operation? I only want to ensure that only 1 Policy gets created?

Thanks,
craig

this is not a NHibernate Question, but I hope this help

you can create a synchronized class/object which the responsibility is to create Policy Object (search the word synchronization in .net or synchronized in java)

this is not the best way to do it.
tj