using System;

using System.Collections.Generic;

​

public class Position {

    private int _row;

    private int _col;

    public Position(int row, int col) {

        this.Row = row;

        this.Col = col;

    }

    public int Row {

        get { return _row; }

        set {

            if (value < 1 || value > 8)

                throw new ArgumentOutOfRangeException("" + value + " is invalid");

            _row = value;

        }

    }

    public int Col {

        get { return _col; }

        set {

            if (value < 1 || value > 8)

                throw new ArgumentOutOfRangeException("" + value + " is invalid");

            _col = value;

        }

    }

    public override String ToString() {

        return "Position(" + Row + "," + Col + ")";

    }

}

​

public class ChessPiece {

    protected Position CurrentPos {

        get;

        set;

    }

    public Position GetPosition() {

        return CurrentPos;

    }

    public ChessPiece(Position startPos) {

        this.CurrentPos = startPos;

    }

    public void Move(Position newPos) {

        List<Position> moves = LegalMoves();

        bool legal = false;

        foreach (Position move in moves) {

            if (move.Row == newPos.Row && move.Col == newPos.Col) {

                legal = true;

            }

        }

        if (legal) 

            this.CurrentPos = newPos;

        else

            throw new Exception("Illegal move!");

    }

    protected virtual List<Position> LegalMoves() {

        return new List<Position>();

    }

}

​

public class Pawn : ChessPiece {

    public Pawn(Position startPos) : base(startPos) {

    }

    protected override List<Position> LegalMoves() {

        List<Position> legalPositions = new List<Position>();

        if (CurrentPos.Row - 1 >= 1) {

            legalPositions.Add(new Position(CurrentPos.Row - 1, CurrentPos.Col));

        }

        return legalPositions;

    }

}

​

public class Program

{

    public static void Main()

    {

        Pawn pawn = new Pawn(new Position(7, 6));

        pawn.Move(new Position(6, 6));

        Console.WriteLine("Pawn is now at " + pawn.GetPosition());

        pawn.Move(new Position(5, 6));

        Console.WriteLine("Pawn is now at " + pawn.GetPosition());

        pawn.Move(new Position(8, 8));

        Console.WriteLine("Pawn is now at " + pawn.GetPosition());

    }

}