How Do You Catch Darkrai On Pokemon Diamond?

The only way to catch darkrai is at the beggining of the game start off with turtwig and then while you are playing make sure you have a garchomp in your party make sure you still have a turtwig on level 45 then you go to Canalave City where there will be a boy having a nightmare about Darkrai when you go to full moon island there will be Cressilia battling Darkrai you will be given the choice in which one you want to catch *I chose Darkrai of course you get him on level 75*

You can get mystery gift and wait for the event, where you get the member card and the stuck door on the house in canalave will open and you can go to new moon island and get darkrai

or you can use the action replay and talk to the sailor's wife where his kid won't wake up from a nightmare about darkrai, then you end up going to full moon island where you can catch cresselai (beware, cresselia might flee, but it's just liek mesprit you can catch it later) and use the action replay setting, 'run through objects/walls/items/whatever' and when you first sail to fullmoon island go all the way to the east/right side of the island and walk over the water until you hit new moon island and you can either kill or catch darkrai there. It will be at level fourty (at least it was for me)

Well, you can't get darkrai without the event in diamond,pearl, and platinum

You need to get an action replay and get the darkrai event code