Fixing CS1525 error with bitboards and returning ulongs

Question

I am building a chess engine and need to use bitboards. I wrote a function that gets the Bitboards, but now I am getting a CS1525 compiler error with the ref statements. Can anyone suggest a workaround? I am still learning about C#. Thank you for any help you can provide.

Here is the function

private ref ulong GetBitboard(Piece.PieceType pieceType)
{
    return ref pieceType switch
    {
        Piece.PieceType.WhitePawn => ref whitePawns,
        Piece.PieceType.WhiteKnight => ref whiteKnights,
        Piece.PieceType.WhiteBishop => ref whiteBishops,
        Piece.PieceType.WhiteRook => ref whiteRooks,
        Piece.PieceType.WhiteQueen => ref whiteQueens,
        Piece.PieceType.WhiteKing => ref whiteKing,
        Piece.PieceType.BlackPawn => ref blackPawns,
        Piece.PieceType.BlackKnight => ref blackKnights,
        Piece.PieceType.BlackBishop => ref blackBishops,
        Piece.PieceType.BlackRook => ref blackRooks,
        Piece.PieceType.BlackQueen => ref blackQueens,
        Piece.PieceType.BlackKing => ref blackKing,
        _ => throw new ArgumentException("Invalid Piece Type"),
    };
}

Answer 1

If the switch expression does not work, then try the switch statement:

private ref ulong GetBitboard(Piece.PieceType pieceType)
{
    switch( pieceType )
    {
        case Piece.PieceType.WhitePawn: return ref whitePawns;
        case Piece.PieceType.WhiteKnight: return ref whiteKnights;
        ... and so no ...
        default: throw new ArgumentException("Invalid Piece Type");
    };
}