What do you say if a guy asks if you're single?

This guy who I'm friends with, asked me that. I thought he might like me, Because he's always liking my statuses and complimenting me in Facebook ("you're really beautiful, you know that?"). I kind of like him. He randomly messaged me on Facebook, asking me if I was single, he said something like "Idk If it's too personal, but are you single?". Yes, I am. What should I reply to him?
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+1 y
He's replied now, saying "Just Wondering".
What do you say if a guy asks if you're single?
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