i have two static classes like this ```cs public static class WhitePieces { ... } public static class BlackPieces { ... } ``` and i'm trying to select between them like this ```cs var pieceClass = sideAttacking == Colour.White ? WhitePieces : BlackPieces; ``` and i'm getting this error: ```yml 'WhitePieces' is a type, which is not valid in the given context ``` why is that?