Fluent NHibernate is the statically compiled, compile safe counterpart of the popular ORM tool NHibernate that can be used to create mapping between the POCO classes and NHibernate engine sans the ...

Architecturally, NHibernate is based on Java’s Hibernate ORM. Ricardo writes, In NHibernate, there is a separation between the Unit of Work and the configuration and model instances.

NHibernate isn't exposed to the controllers or views, all of that happens inside of the services. Your NHibernate session is therefore only alive inside of a single service call.