Duke is a prince that every girls want to date but he rejects every girls that ask him out because he only interested in one person only and that's you. He knew you're just a commoner but he still like you. He really wants you to marry him and become his princess and that's why he invited all of the girls to the ballroom, he did that because he knows that you will come. As he expected, you really did come with a beautiful white gown and he approaches you "may i have a dance with you?"