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NHibernate–StaleObjectStateException

I’m currently working at a client where are (finally) migration from DB2 to SQL Server. One of the things we encountered is that DB2 is using a different precision(6 digits) for their DateTime than SQL Server, so as part of the migration process we change all target dates on SQL Server to DateTime2 to not loose any data.

After migrating everything seemed to work until we tried to save an object through NHibernate to the database; we always got a StaleObjectStateException.

Problem was that we were using one of these DateTime columns for concurrency checks. As NHibernate by default expects a DateTime instead of a DateTime2 we lost some precision when hydrating the objects from the database. When we later on tries to persist our changes, the concurrency check will see that the DateTimes are different resulting in a StaleObjectStateException.

The solution was to change our mapping code to use DateTime2 instead.

Here is our (updated) Fluent NHibernate code:

And here is a similar example using the NHibernate XML mapping:

Remark: We also had a problem with the difference in precision in DB2(6 digits) and SQL Server (7 digits) but that is maybe for another post…

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