Hi,

I have a client that communicates to a long-running NH session via a web service, and I am using versioning to enforce optimistic locking.

When an object is successfully updated in the DB, its version number is incremented, which then renders the client-side version stale. So the client-side version number needs to be synchronized, otherwise the client will not be able to do any more updates.

The obvious solution is to send the entire updated object back down to the client to replace the original one, but this could be cumbersome depending on the complexity of the object. I had thought about simply incrementing the version in the client if the update is successful, but the version number is not updated unless the object differs from the one in the NH session.

So I was wondering if anyone had any thoughts on how to handle synchronizing version numbers in an efficient manner?

TIA,
Dean.

I'm not particularly clever with NH yet and not sure of your design decision, but couldn't you place an NHibernate interceptor on the object and keep a flag that an update has occurred? That flag would then tell you to update the version number on the client. Or alternatively just re-retrieve the object and return the updated version number every time?

Kerry,

Thanks for the suggestion about interceptors, I think that might work.
When a particular object is updated, I could record the fact, and then send a list of updated objects back to the client so that it can update the version numbers.

The only other alternative I think is, as you say, to send back the entire object itself but this could have performance issues if objects are bulky.
:D

I hope that you understand that you are working around the problem (and it can became a problem later).

If you are doing this only for "performance" reasons, make sure that it is really a performance issue before doing an "optimization".

KPixel,

Thanks for the warning.
After some discussion, we have decided that we will initially return the entire (updated) object to the client so that the version numbers can be kept in synch.
As you say, if this method turns out to be causing performance issues, then we will go the extra step and put in interceptors.