If your dandruff is just flaky scalp - from dryness - an oil or good moisturizing conditioner - massaged into the scalp -will help.
If it is true dandruff and caused by bacteria or fungus it will take something stronger to fight it.
Here's an article I wrote for the Hair site a few years ago
Dandruff ! A long time ago oil treatments came in capsules and needed to be heated. Oils now are much more refined, do a great job fighting dry or frizzy hair, and don't need to be rinsed off.