NHibernate: Criteria expression to retrieve non-null one-to-one associated class

Question

I have two classes that are associated with a one-to-one mapping:

<class name="Employee" table="Employees"> ... <one-to-one name="Address" class="AddressInfo"> ... </class>

I would like to use a criteria expression to get only Employees where the the associated Address class is not null, something like this (which I know doesn't work):

IList employeesWithAddresses = sess.CreateCriteria(typeof(Employee)) .Add( Expression.IsNotNull("Address") ) .List();

I guess this is either a really difficult question or almost no one has tried to do this?

Co-worker here, with some additional info. This query does not generate an error or anything. It just returns results without filtering out the ones where Address is null. The result set contains entries with both null and not-null values for Address. — Moskie
– Moskie, Commented Nov 24, 2008 at 21:59

Quibblesome · Accepted Answer · 2008-11-27 13:33:39Z

Have you tried creating an alias for the Address property and checking if the ID/primary key of the Address is not null?

Something like:

IList employeesWithAddresses = sess.CreateCriteria(typeof(Employee)) .CreateCriteria("Address", "address").Add( Expression.IsNotNull("Id") ) .List();

Quibblesome · Accepted Answer · 2008-11-27 13:34:17Z

To implicitly trigger a Alias/Join for one-to-one, shouldn't you use dot-notation? And then checking any field in your Address-class:

IList employeesWithAddresses = sess.CreateCriteria(typeof(Employee)) .Add( Expression.IsNotNull("Address.Id") ) .List();

This is probably the same approach as Kareena, but I believe this is equal to .CreateAlias(). With CreateAlias you can specify FetchMode (the type of join used) but since you want rows with corresponding Addresses, that shouldn't be nessecary (because INNER is default). Nor should it be nessecary to check if it's null.

IList employeesWithAddresses = sess.CreateCriteria(typeof(Employee)) .CreateAlias("Address") .List();

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