You would be far better prepared to refute the claims made in the DaVinci Code by buying and reading one of the well written, well researched claim by claim Christian rebuttals on the DaVinci Code.
Just reading the book isn't going to prepare you with facts you need to refute the false conspiracy claims found in the book and putting money in their pockets by buying the book or seeing the movie isn't going to help either.
You don't need to read the fictional story to properly deal with the false claims made within.