Say that you're flattered, thank you. But I am not looking to date right now so thank you very much but I have to turn you down.
They might persist a little, but smile, be polite but DO NOT get guilttripped into it. If you feel a little cornered or offended, you can say you are a girl who knows what you want and this is not something you want now. So sorry but that's how it is. I'm sure you're a nice guy but I am not looking -- for anything. They might try to convince u it can mean nothing, just for fun, doesn't have to be a 'thing'. Then just smile and say no and shake your head. At this point u don't have to explain anymore. Just no, shake head, no shake head. He'll let it go. Smile and it makes everything softer. Hope that helps!