filter entitydatasource organization value

i unequivocally entity framework, nonetheless there pivotal pieces plea me. anyone tell me filter an entitydatasource an organization column? ef hides fk values instead an organization property. given an entity, person, persontype association, i have approaching something work i wish filter chairman entity type:

griddatasource.entitytypefilter = "it.persontype.persontypeid = 1";

or

griddatasource.where = "it.persontype.persontypeid = '1'";

or even

griddatasource.whereparameters.add(new parameter("it.persontype.persontypeid", dbtype.object, "1"));

but zero those work. anybody know this?