How is a "cause of action" determined under res judicata?

For purposes of applying the res judicata doctrine, a "cause of action" is determined under the primary right theory. "The primary right theory . . . provides that a 'cause of action' is comprised of a 'primary right' of the plaintiff, a corresponding 'primary duty' of the defendant, and a wrongful act by the defendant constituting a breach of that duty. [Citation.] The most salient characteristic of a primary right is that it is indivisible: the violation of a single primary right gives rise to but a single cause of action. [Citation.] . . . [] As far as its content is concerned, the primary right is simply the plaintiff's right to be free from the particular injury suffered. [Citation.] It must therefore be distinguished from the legal theory on which liability for that injury is premised: 'Even where there are multiple legal theories upon which recovery might be predicated, one injury gives rise to only one claim for relief.' [Citation.]" (Crowley v. Katleman (1994) 8 Cal.4th 666, 681-682, italics omitted.)