I am seeing a Dairy Creek in the Willamette Zone near Forest Grove, with west and east forks, there are no Exceptions listed for it which means it follows the Zone Regs.
That means it is open May 22 to Oct.31, the rest of the year it is closed to fishing. When open for Trout (C&R only except Brook and Brown Trout, flies and lures only), it is also open for bass and all the fish in the list that starts with 'Bluegill'.