Hi

We are currently investigating the feasibility of moving from our existing ORM vendor to NHibernate. One of the features of our existing ORM is that it supports the concept of nested unit of works. If the nested unit of work commits, the changes made are committed back into the parent unit of work and vice versa. All of this happens in memory and it is only when you commit the root unit of work that the changes are committed within a db transaction to the database. This gives us the ability to have multi-level undo functionality in our application which is one of our usability requirements.

I see that the ISession in NHibernate maps to the concept of a unit of work. I am however unable to assess with my current limited knowledge of NHibernate whether it is possible to accomplish the same nested unit of work functionality using NHibernate. Is this possible? How would one go about implementing this with NHibernate?

Thanks
Carel

Hello...

I think NHibernate will not support this for you. A Unit of Work should be a very short-lived thing, and not span any User Input. So I guess you need something else here.

Something you COULD look at is the CSLA framework. This Framework has a multi Level Undo implemented in its base Classes, and allows you to achieve exactly what you want. Also it can be used with NHibernate.

The "job" of CSLA is not persistence, but the Business Logic, so the 2 worlds wont have many overlaps. You can look at a recent DNRTV Episode to see a discussion about extracting the DAL from the framework and use DTO to load/save the data.