Fraternity formal outfit

So i bought a basic black amd silver bodycon dress that fits perfectly and isnt too short or tight or trashy. I showed my bf and he just didnt think it was formal enough. Granted i had no bra on and would wear heels. Its a short formal dress occasion not long. So thats why my bf wasnt sure he thought that it was long a long prom dress. My question is for anyone who has ever been isnt a basic black dress good? I don't need an over the top drsss roght??