I would like to know if there is a way to disable automatic loading of child records in nHibernate ( for one:many relationships ).
We can easily switch off lazy loading
You can have the lazy attribute on the collection. In your example, Department has n employees, if lazy is enabled, the employees will not be loaded by default when you load a department : http://www.nhforge.org/doc/nh/en/#collections-lazy
You can have queries that explicitly load department AND employees together. It's the "fetch" option : http://www.nhforge.org/doc/nh/en/#performance-fetching-lazy