I\'m using two class NiceCustomer & RoughCustomer which implment the interface ICustomer.
The ICustomer has f         
        
It is not possible to map an interface in nhibernate. If your goal is to be able to query using a common type to retrieve both types of customers you can use a polymorphic query. Simply have both your classes implement the interface and map the classes normally. See this reference:
https://www.hibernate.org/hib_docs/nhibernate/html/queryhql.html (section 11.6)