Invite people to the party

Example 1

You : Would you like to join us in the party tonight?
Friends : Sure.
You : Ok. See you at Peter's house tonight at 9 pm.

Example 2

You : Are you coming to the party tonight?
Friend : I'm afraid not.
You : How come?
Friend : I have to study for an exam tomorrow.
You : Well. In that case, I will have to let you go.
Friend : Sorry. Maybe next time.

Example 3

You : Do you want to join the party tonight?
Friend : I wish I could but I have to visit my grandmother.
You : That's alright.