Can I ask this guy to be my badminton partner?

[nmyankee]

Good that you haven't added him to msn or facebook - you shouldn't add any guys until after they've put you on their contacts.
Now - as far as a badminton partner goes, you haven't said what year you're in at school, nor what year he's in and neglected, also, to say how old each of you are. If you're 14, and he's 16, I would advise you to not ask as, even if he likes you. he would probably refuse due to anticipated peer pressure. It would also seem odd, if he does play badminton but isn't good at it, that you would ask him to be your partner. There's nothing to stop you, however, from telling him that you're looking for a partner and wonder if he knows of anyone who might be interested. This gives him the opportunity to volunteer so won't make him feel uncomfortable which might happen if you directly asked him to partner you.