Recently had an interesting experience with NHibernate (I was against working with it from the beginning for many reasons, but unfortunately I wasn't the one to decide). I added trigger to a table that performs several update / insert operation to other tables. Suddenly updating table via NHibernate returned error:

NHibernate.AdoNet.TooManyRowsAffectedException: Unexpected row count: 6; expected: 1

So NHibernate doesn't support triggers that perform DML operations? Not quite. The solution is: add SET NOCOUNT ON before trigger performs DML operations. Looks like NHibernate doesn't really count DML operations, but messages of the type "2 rows updated" returned by SQL Server. And NOCOUNT setting suppresses these messages.