Find the maximum area of figure of 1 in matrix

using System;
using System.Linq;
namespace DictionaryLKSH
{
    class MainClass
    {
        static void fun(int[][] field, int Cx, int Cy, ref bool[,] checker, ref int answer)
        {
            answer++;
            checker[Cx, Cy] = false;
            if (checker[Cx, Cy] == false && checker[Cx + 1, Cy] == false && checker[Cx - 1, Cy] == false && checker[Cx, Cy + 1] == false && checker[Cx, Cy - 1] == false)
                return;
            else
            {
                if (checker[Cx + 1, Cy])
                {
                    checker[Cx + 1, Cy] = false;
                    fun(field, Cx + 1, Cy, ref checker, ref answer);
                }

                if (checker[Cx - 1, Cy])
                {
                    checker[Cx - 1, Cy] = false;
                    fun(field, Cx - 1, Cy, ref checker, ref answer);
                }

                if (checker[Cx, Cy + 1])
                {
                    checker[Cx, Cy + 1] = false;
                    fun(field, Cx, Cy + 1, ref checker, ref answer);
                }

                if (checker[Cx, Cy - 1])
                {
                    checker[Cx, Cy - 1] = false;
                    fun(field, Cx, Cy - 1, ref checker, ref answer);
                }
            }
        }

        public static void Main(string[] args)
        {


            int[] TempArray = Console.ReadLine().Split(' ').Select(e => Convert.ToInt32(e)).ToArray();
            int n = TempArray[0] + 2, m = TempArray[1] + 2;
            int[][] Field = new int[n][];
            int answer = 0;
            int realAnswer = 0;
            for (int i = 0; i < n; i++)
                Field[i] = new int[m];
            bool[,] checker = new bool[n, m];
            for (int i = 0; i < n; i++)//wall of 2
                for (int j = 0; j < m; j++)
                {
                    if (i == 0 || i == n - 1 || j == 0 || j == m - 1) Field[i][j] = 2;
                    else Field[i][j] = 0;
                }
            for (int i = 1; i < n - 1; i++)//fill the mass
            {
                TempArray = Console.ReadLine().Split(' ').Select(e => Convert.ToInt32(e)).ToArray();
                for (int j = 1; j < m - 1; j++)
                {
                    Field[i][j] = TempArray[j - 1];
                }
            }
            for (int i = 0; i < n; i++)//hcecker
                for (int j = 0; j < m; j++)
                    if (Field[i][j] == 1) checker[i, j] = true;//shoulde be checked
                    else checker[i, j] = false;//checked

            for (int i = 1; i < n - 1; i++)//search
            {
                for (int j = 1; j < m; j++)
                {
                    if (checker[i, j])
                    {
                        fun(Field, i, j, ref checker, ref answer);
                        if (answer > realAnswer)
                        {
                            realAnswer = answer;
                        }
                        answer = 0;
                    }
                }
            }
            Console.WriteLine(realAnswer);
        }
    }
}
/*
6 10
1 1 0 0 0 0 0 1 1 0
0 1 1 1 0 1 0 1 1 0
0 1 1 0 1 0 1 0 1 0
0 1 0 1 0 1 0 1 1 0
0 1 1 1 0 0 1 1 1 0
0 0 0 0 0 0 0 0 0 0
*/