Can i join dawnguard but still get the vampire lord somehow. becuase i want to. Be a badass vamp lord but i dont want to block out the sun

This has been discussed already.

Nobody knows.

I hope not.

Vampires joining the Dawnguard...

Wouldn't that be like a Nun joining a prostitution ring?

pretty sure, you cannot without use of mods

Or a prosttute joining a Nunnery. Both are equally improbable, same as being a Vampiric Vampire-hunter.

Although, people have told me straaange stories...

Solution, OP? Make two characters or make your mind up.

EDIT: OP, have a fishy stick! http://www.imperial-library.info/sites/default/files/dogate_til_fishystick.jpg

Somehow I doubt the Dawnguard would let one of the very things they are hunting be amongst their ranks.
Vampire Hunters don't look favorably upon Vampires.

Well, there have been vampires who join vampire hunters. But I don't think you can be a vampire lord and be a vampire hunter

Let alone the other way around; why would a Vampire Lord give you his powers if you're hunting him...?

According to some E3 reviewers, you can join the vampires but you don't have to side with Harkon and the whole block out the sun thing if that's what worries you.

Because you've asked nicely?