Hi.

I have several working threads. Every thread can add data to datebase. It is possible situation when the same bussines entity will be added to datebase by two threads in the same time. So after that I have two copies of the one entity with different identificators.

Can NHibernate help to deal with that? Is it my job?

Yes, hibernate can help you there:

http://nhforge.org/doc/nh/en/index.html#transactions

In short words, you can add versioning columns to your entities and hibernate will handle this for you. You then get exceptions when you try to save modifications and don't have the newest version. Addionally there is a "select-before-update" flag, you can add to the class mapping.

But that only solves the issues when you try to modify entries. If you want consistent objects in all threads you have to think about using hibernate caching:

http://nhforge.org/doc/nh/en/index.html#performance-cache

In my case the same business entity does not mean the same business class. Threads do not share entity pool. Every thread creates entities. So if two threads create the same entity at the same time... I guess second level cache is useless in such situation. Maybe I got something wrong.

Afaik the cache operates or can operate across threads. So each of you thread would check the cache first and then if necessary load the object. But I'm not sure about that.