How to send copy of array in c# [duplicate]

Question

• So, I'm trying to make simple Console Tic Tac Toe Game, with AI.
• Current board state is stored inside multi-dimensional array.
• To check what the best move for AI is, im using recursion.
• The function "CheckMove" changes board position, and then calls itself to see where it goes.
• But the problem is that if i change board state inside called function, it will also change inside a caller.

How to avoid that? Simplified code:

static void Main()
    {
        int[] board = { 1 };
        CheckMove(board);
        //board = 2
    }

    static void CheckMove(int[] board)
    {
        board[0] = 2;
    }

full code (WIP):

enum Sym
{
    E, X, O
}

class Program
{
    static void Main(string[] args)
    {
        Sym[,] board = new Sym[3,3];
        int x, y;
        while (End(board) == 2)
        {
            Display(board);

            Console.WriteLine("Make your move - column: ");
            x = Convert.ToInt32(Console.ReadLine())-1;
            Console.WriteLine("Make your move - row: ");
            y = Convert.ToInt32(Console.ReadLine())-1;

            board[y, x] = Sym.X;

            int[,] chances = new int[3, 3];

            for (int i = 0; i < 3; i++)
                for (int j = 0; j < 3; j++)
                {
                    chances[i, j] = CheckMove(board, i, j, true);
                }
        }
        Display(board);
        Console.WriteLine("GG");
        Console.WriteLine("____________________________________________________________");

        Console.ReadLine();
    }

    static void Display(Sym[,] board) //Displays whole board
    {
        for (int i = 0; i < 3; i++)
        {
            Console.WriteLine($"{board[i,0]} {board[i,1]} {board[i,2]}");
        }
    }

    static int End(Sym[,] board) //Chcecks if the game shall end (-1 player won) (0 tie) (1 cpu won) (2 game in progress)
    {
        bool Full = true;

        for (int i = 0; i < 3; i++)
        { //This part is currently broken
            if (board[i, 0] == Sym.E || board[i, 1] == Sym.E || board[i, 2] == Sym.E) Full = false;
            if (board[i, 0] == board[i, 1] && board[i, 1] == board[i, 2] && board[i, 0] == Sym.X) return -1;
            if (board[0, i] == board[1, i] && board[1, i] == board[2, i] && board[0, i] == Sym.X) return -1;
            if (board[i, 0] == board[i, 1] && board[i, 1] == board[i, 2] && board[i, 0] == Sym.O) return 1;
            if (board[0, i] == board[1, i] && board[1, i] == board[2, i] && board[0, i] == Sym.O) return 1;
        }
        if (board[0, 0] == board[1, 1] && board[1, 1] == board[2, 2] && board[0, 0] == Sym.X) return -1;
        if (board[0, 0] == board[1, 1] && board[1, 1] == board[2, 2] && board[0, 0] == Sym.O) return 1;
        if (board[2, 0] == board[1, 1] && board[1, 1] == board[0, 2] && board[2, 0] == Sym.X) return -1;
        if (board[2, 0] == board[1, 1] && board[1, 1] == board[0, 2] && board[2, 0] == Sym.O) return 1;

        if (Full == true) return 0;
        return 2;
    }

    static int CheckMove(Sym[,] board, int a, int b, bool cpuTurn) //Check how good subjected move is
    {
        if (board[a, b] == Sym.E)
            if (cpuTurn == true) board[a, b] = Sym.O;
            else board[a, b] = Sym.X;
        else return 0;

        if (End(board) != 2) return End(board);

        int Value = 0;

        for (int m = 0; m < 3; m++)
            for(int n = 0; n < 3; n++)
            {
                Value += CheckMove(board, m, n, !cpuTurn);
            }
        return Value;
    }
}

Answer 1

As far as I can see, you have problems with 2D array Sym[,] in the

static int CheckMove(Sym[,] board, int a, int b, bool cpuTurn)

method; since board is 2D array, typical solutions like board.ToArray() don't work (they don't even compile). Try Clone() the board instance:

// Let's rename board into value...
static int CheckMove(Sym[,] value, int a, int b, bool cpuTurn) {
  // ... in order to preserve all the other code:
  // we are now working with the copy of the passed board
  Sym[,] board = value.Clone() as Sym[,];

  // Your code from CheckMove here
  ... 
} 

Since Sym is a enum (i.e. a value type), shallow copy is enough