Flood fill - count island - code review - make the code less verbose, extra a visit neighbor function - four directions neighbors

FloodFill_countIsland_codereview2.cs

using System;
using System.Collections.Generic;

class LearningExperience {
   static void Main(string[] args) {
      Console.WriteLine("Meet a new person and talk about flood fill algorithm");
   }
   
   public static int CountIsland(int[][] matrix)
   {
      if(matrix == null || matrix.Length == 0 || matrix[0].Length==0) return 0; 
      
      int rows = matrix.Length; 
      int cols = matrix[0].Length; 
      
      int islandCount = 0; 
      for(int row = 0 ; row < rows; row++)
      {
         for(int col = 0; col < cols; col++)
         {
            var current = matrix[row][col]; 
            
            if(current != 1) continue; 
            
            visitIslandBFS(matrix, row, col); 
            islandCount ++; 
         }
      }
      
      return islandCount; 
   }
   
   private static void visitIslandBFS(int[][] matrix, int row, int col)
   {
      Queue<string> queue = new Queue<string>(); 
      
      var key = encodeKey(row,col); 
      queue.Enqueue(key); 
      
      while(queue.Count > 0)
      {
         var current = queue.Dequeue(); 
         var positions = Array.ConvertAll(current.Split('+'), int.Parse);  // decode the key 

         int visit_row = positions[0];
         int visit_col = positions[1]; 
         
         matrix[visit_row][visit_col] = 2; 
         
         // left 
         visit(matrix, visit_row, visit_col, 0, -1, queue); 
         
         //right
         visit(matrix, visit_row, visit_col, 0, 1, queue); 
         
         // top
         visit(matrix, visit_row, visit_col, -1, 0, queue); 
         
         // bottom
         visit(matrix, visit_row, visit_col, 1, 0, queue);                    
      }
   }

   /// <summary>
   /// visit function is to visit the neighbor nodes in four directions, left, right, top and bottom
   /// </summary>
   /// <param name="matrix"></param>
   /// <param name="row"></param>
   /// <param name="col"></param>
   /// <param name="incrementX"></param>
   /// <param name="incrementY"></param>
   private static void visit(int[][] matrix, int row, int col, int incrementX, int incrementY, Queue<string> queue)
   {
       int neighbor_row = row + incrementX;
       int neighbor_col = col + incrementY; 

       if(isInBoundary(matrix, neighbor_col, neighbor_col)
       {
           var neighborKey = encodeKey(neighbor_row, neighbor_col); 
           queue.Enqueue(neighborKey); 
       }
   }

   private static string encodeKey(int row, int col)
   {
      return row +"+"+ col;
   }
   private static bool isInBoundary(int[][] matrix, int row, int col) 
   {
      int rows = matrix.Length; 
      int cols = matrix[0].Length; 
      
      return (row >= 0 && row < rows && col >=0 && col < cols); 
   }
}