Where i get darkrai? pokemon diamond?

hey you should know me and to get darkrai is to beat the elite4 and then get the national dex and then go to canaclave city and go 2 sailor edrith's house you'll find a sick boy in bed about bad nightmares go 2 the sailor near the house and talk to him to bring you 2 full moon island and meet cresslia and then get the lunar wing but make sure you saved before going to the island and then go back give the boy the wing to cure him and then go to the poke market talk to the cashier where you purchased items and he'll give you a members card then you go 2 the harbor's inn then you'll know wat happens when your in there oh my friend code is 0430 4958 9686 and name is Alvin