Hibernate and Log4J are a de-facto standard of ORM (Object-relational mapping) and logging (respectively) in Java world. That's why both were ported to .NET runtime environment.
NHibernate is ORM solution and is intended for transparent binding .NET classes to database tables. NHibernate was designed to reduce time efforts to switch application to another database provider. It is achieved by means of replacing SQL with special NHibernate query language (HQL), providing dialects for several databases and providing special classes for retrieving/updating data in database.
Log4Net is logging framework which is useful for tracking errors in application and can write logs either to database table or flat files. You can download sample Visual Studio .NET project here
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