ChessDotNet.ChessGame.GetFen C# (CSharp) Method

        public virtual string GetFen()
        {
            StringBuilder fenBuilder = new StringBuilder();
            Piece[][] board = GetBoard();
            for (int i = 0; i < board.Length; i++)
            {
                Piece[] row = board[i];
                int empty = 0;
                foreach (Piece piece in row)
                {
                    char pieceChar = piece == null ? '\0' : piece.GetFenCharacter();
                    if (pieceChar == '\0')
                    {
                        empty++;
                        continue;
                    }
                    if (empty != 0)
                    {
                        fenBuilder.Append(empty);
                        empty = 0;
                    }
                    fenBuilder.Append(pieceChar);
                }
                if (empty != 0)
                {
                    fenBuilder.Append(empty);
                }
                if (i != board.Length - 1)
                {
                    fenBuilder.Append('/');
                }
            }

            fenBuilder.Append(' ');

            fenBuilder.Append(WhoseTurn == Player.White ? 'w' : 'b');

            fenBuilder.Append(' ');

            bool hasAnyCastlingOptions = false;


            if (CanWhiteCastleKingSide)
            {
                fenBuilder.Append('K');
                hasAnyCastlingOptions = true;
            }
            if (CanWhiteCastleQueenSide)
            {
                fenBuilder.Append('Q');
                hasAnyCastlingOptions = true;
            }


            if (CanBlackCastleKingSide)
            {
                fenBuilder.Append('k');
                hasAnyCastlingOptions = true;
            }
            if (CanBlackCastleQueenSide)
            {
                fenBuilder.Append('q');
                hasAnyCastlingOptions = true;
            }
            if (!hasAnyCastlingOptions)
            {
                fenBuilder.Append('-');
            }

            fenBuilder.Append(' ');

            DetailedMove last;
            if (Moves.Count > 0 && (last = Moves[Moves.Count - 1]).Piece is Pawn && Math.Abs(last.OriginalPosition.Rank - last.NewPosition.Rank) == 2
                && last.OriginalPosition.Rank == (last.Player == Player.White ? 2 : 7))
            {
                fenBuilder.Append(last.NewPosition.File.ToString().ToLowerInvariant());
                fenBuilder.Append(last.Player == Player.White ? 3 : 6);
            }
            else
            {
                fenBuilder.Append("-");
            }

            fenBuilder.Append(' ');

            fenBuilder.Append(_halfMoveClock);

            fenBuilder.Append(' ');

            fenBuilder.Append(_fullMoveNumber);

            return fenBuilder.ToString();
        }