It's courteous for the guy to pay for the meal. It may be a little sexist, but I do think we should have these gender rules that are just a nice gesture towards a person. Even if the date was an utter disaster then you should at least offer to pay.
If the woman offers to pay then you must refuse, if she persists then you must agree on the condition that you do something else to make it fair.
If the woman offers to pay then you must refuse, if she persists then you must agree on the condition that you do something else to make it fair.