Write same idea from code using queue

ConnectedCellInaGridCopy1.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConnectedCellInaGrid2
{
    class Program
    {
        static void Main(string[] args)
        {   // 2:40pm - 3:08pm 
            int row = Convert.ToInt32(Console.ReadLine());
            int col = Convert.ToInt32(Console.ReadLine());

            char[,] arr = new char[row, col]; 

            for(int i=0;i< row; i++)
            {                 
                    string s = Console.ReadLine();                    

                    int j = 0; 
                    foreach (char c in s)
                    {
                        if(c=='0' || c=='1')
                        {
                            arr[i,j] = c;
                            j++; 
                        }
                    }
                               
            }

            int max = 0; 
            for(int i = 0; i < row; i++)
                for (int j = 0; j < col; j++)
                {
                    int cur = getRegionCount(arr, i, j, row, col);
                    if (cur > max)
                        max = cur; 
                }

            Console.WriteLine(max); 
        }

        public static int getRegionCount(char[,] arr, int startX, int startY, int row, int col )
        {
            char c = arr[startX, startY]; 
            if(c == '0' || c =='2')
                return 0; 

            Queue<int> queue = new Queue<int>(); 
            
            queue.Enqueue(getKey(startX, startY));

            int[] dneighbor = { -1, 0, 1 };

            int retCount = 0; 
            while(queue.Count > 0 )
            {
                int key1 =(int) queue.Dequeue();
                int x = key1 / 10;
                int y = key1 % 10;

                if (arr[x, y] == '1')  // need to add the check, otherwise, count more than once 
                {
                    arr[x, y] = '2'; // visited
                    retCount++;
                }

                for(int i=0; i< dneighbor.Length; i++)
                    for (int j = 0; j < dneighbor.Length; j++)
                    {
                        int nx = x + dneighbor[i];
                        int ny = y + dneighbor[j];

                        if (nx >= 0 && nx < row && ny >= 0 && ny < col && arr[nx, ny] == '1')                        
                        {
                            queue.Enqueue(nx * 10 + ny);
                        }
                    }
            }

            return retCount; 
        }

        private static int getKey(int x, int y)
        {
            return 10 * x + y; 
        }
    }
}