What will you do if you saw your ex on the street and ur w/ ur current man/woman

I would feel betrayed by my current bf. I would have no expectations from my ex but I would be disappointed in my current. Cheating is one betrayal that I simply cannot handle. Although if my bf was cheating on me with my ex (in a gay relationship as they are both men) I might feel a little better because then it's like if my bf is gay then we had no real chance together anyway and I would be glad to be finding out sooner than later. It would also mean that I need to work on my judgment on what kind of men to date. But if they were just friends then it would just make me feel awkward.