If you know the XNA api you might want to try SharpDX. It's more or less a clone of the DirectX api, like XNA is, but it currently supports up to DirectX 11.1. Also most of the library locations are somewhat similar so it's not too bad to convert.
I can't remember the name but I think there is another C#/DirectX based library if SharpDX doesn't float your boat.
EDIT: I was thinking of SlimDX, but it is out of date.