We have Oracle 11 as database for our third party server application. The interactions for db is only allowed through the interops DLLs provided by vendor. No direct access to database is allowed. We need to connect to the database using those DLLs for creating or deleting objects inside the database. I am wondering if I can use Nhibernate by writing some wrappers about those DLLs. No SQL queries are also allowed. Can this be done?
Who is vendor? Not Oracle I guess, but your "third party" providing the "application server" software.
In such case this looks like they want to forbid direct SQL access to their application DB. So there is no point trying to use an ORM such as NHibernate, it would be from their point of view almost like directly querying the DB.
Your "best" option is to ask them if they can provide their own NHibernate database driver, but their answer will very probably be "No".