study the code

ConnectedCellInaGrid5.cs

using System;
using System.Collections.Generic;
using System.IO;
class Solution {
    static void Main(String[] args)
        {
            /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
            int row = Convert.ToInt32(Console.ReadLine());
            int col = Convert.ToInt32(Console.ReadLine());
            int[,] arr = new int[row, col];
            bool[,] marked = new bool[row, col];
            for (int i = 0, j = 0; i < row; i++)
            {
                j = 0;
                foreach (string str in Console.ReadLine().Split(' '))
                {
                    arr[i, j] = Convert.ToInt32(str);
                    j++;
                }
            }
            int count;
            int result=0;
            for (int i = 0; i < row; i++)
            {
                for (int j = 0; j < col; j++)
                {
                    if (marked[i, j] == false && arr[i, j] == 1)
                    {
                        count = Calculate(arr, marked, i, j);
                        if (count > result)
                        {
                            result = count;
                        }
                    }
                    else
                    {
                        marked[i, j] = true;
                    }
                }
            }
            Console.WriteLine(result);
            Console.ReadLine();

        }
        static int Calculate(int[,] arr, bool[,] marked, int row, int col)
        {
            if (row < 0 || col < 0 || row >= arr.GetLength(0) || col >= arr.GetLength(1))
            {
                return 0;
            }
            if (marked[row, col] == false && arr[row, col] == 1)
            {
                marked[row, col] = true;
                return 1 
                    + Calculate(arr, marked, row - 1, col)
                    + Calculate(arr, marked, row - 1, col - 1)
                    + Calculate(arr, marked, row - 1, col + 1)
                    + Calculate(arr, marked, row, col - 1)
                    + Calculate(arr, marked, row, col + 1)
                    + Calculate(arr, marked, row + 1, col - 1)
                    + Calculate(arr, marked, row + 1, col)
                    + Calculate(arr, marked, row + 1, col + 1);
            }
            else
            {
                marked[row, col] = true;
                return 0;
            }
        }            
    
}