NHibernate: "NHibernate is a .NET based object persistence library for relational databases. NHibernate is a port of the excellent Java Hibernate relational persistence tool.
(If you are courious about what is Hibernate: Hibernate is a powerful, ultra-high performance object/relational persistence and query service for Java. Hibernate lets you develop persistent classes following common Java idiom - including association, inheritance, polymorphism, composition and the Java collections framework. The Hibernate Query Language, designed as a 'minimal' object-oriented extension to SQL, provides an elegant bridge between the object and relational worlds. Hibernate also allows you to express queries using native SQL or Java-based Criteria and Example queries.) "