§ 13–502. Effect of assignment.

When cross-demands have existed between persons under such circumstances that if one had brought an action against the other a counterclaim could have been pleaded, neither can be deprived of the benefit thereof by an assignment by the other; but in an action by the assignee of a nonnegotiable debt the defendant may set off by counterclaim any indebtedness to him of the assignor, existing before notice of the assignment, as well as any indebtedness to him of the plaintiff.