nHibernate, No row with the given identifier exists

I have a mapping along the lines of this.

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="Model.Entities" schema="etl" assembly="Model" default-lazy="false">
  <class name="Model.Entities.DataField, Model" table="mdm_field">
    <id name="FieldId" column="field_id" type="int">
      <generator class="native" />
    </id>
    <many-to-one name="KeyField" class="Model.Entities.Key, Model" column="field_id" />
  </class>
</hibernate-mapping>

Now in the database the field_id in the mdm_field table sometimes has a value that does not exist in the related key_field table, so it is basically broken referential integrity. Because of this when I load the entity I get an error "No row with the given identifier exists". How do I configure the mapping to work with this situation so it will not die on this situation.

Ok, I found the answer. Add the

not-found="ignore"

attribute to the property KeyField:

<many-to-one name="KeyField" not-found="ignore" class="Model.Entities.Key, Model" column="field_id" />

In my case the problem was because a foreign key constraint was not enforced by MyISAM engine and therefore one of the rows ended up pointing to a non-existant value and the proxy threw an exception. I would recommend checking your dataset is consistent in this case.

Try that...

public void Override(ModelMapper modelMapper) {
    modelMapper.Class<T>(c => { 
        c.ManyToOne(m => m.FKObj, r => {
            r.Column("FKColumn");
            r.NotFound(NotFoundMode.Ignore); // THIS IS IMPORTANT!!!
        });
    });
}