I am working with a few legacy tables that have relationships, but those relationships haven\'t been explicitly set as primary/foreign keys. I created a .dbml file using \"
Is the association set to One to One or One to Many? If you have the association set to One to Many, then what you have is an EntitySet, not an EntityRef and you'll need to use a where clause on the dependent set to get the correct value. I suspect that you want a One to One relationship, which is not the default. Try changing it to One to One and see if you can construct the query.
Note: I'm just guessing because you haven't actually told us what the "trouble" actually is.