NHibernate is an ORM (object relation mapper) for .NET inspired by Hibernate.

In these code examples I will use the basic xml configuration.

Relationships

Relationships in NHibernate are very tightly related to relationships in a SQL database.

One to Many Associations

• One to Many Relationships

** <set><one-to-many class="Order"/></set> ** two tables and an FK CustomerId in Order table

• Many to One Relationship

** <many-to-one name="Customer"/>

• Many to many

** two tables and an FK CustomerId in Order table ** <many-to-many/> ** joining table with two FKs, one to each related table

<!-- Customer -->
<set name="Orders" table="`Order`">
    <key column="CustomerId"/>
    <one-to-many class="Order" />
</set>
<set name="Addresses" table="Address">
    <key column="CustomerId"/>
    <many-to-many column="AddressId" class="Address"/>
</set>

<!-- Order -->
<many-to-one name="Customer" column="CustomerId"/>

One to One Association

Relationship where two tables share the same PK.

<!-- Customer -->
<one-to-one name="Person"/>

References

• NHibernate Fundamentals at Pluralsight