Generating Contaminant Array, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            int row = 5;
            int column = 5;

string[,] arr = new string[,]
            {
                { "W", "W", "W", "R", "W" },
                { "C", "R", "R", "R", "R" },
                { "R", "W", "W", "R", "W" },
                { "W", "W", "W", "R", "R" },
                { "W", "R", "R", "W", "C" }
            };
            
            string[,] result = GenerateContaminant(row, column, arr);

for (int rowValue = 0; rowValue < result.GetLength(0); rowValue++)
            {
                for (int colValue = 0; colValue < result.GetLength(1); colValue++)
                {
                    Console.Write(result[rowValue, colValue]);
                }
                Console.WriteLine();
            }
        }
        
        public static string[,] GenerateContaminant(int row, int column, string[,] arr)
        {
            string[,] result = new string[row, column];
            for (int i = 0; i < row; i++)
            {
                for (int j = 0; j < column; j++)
                {
                    result[i, j] = arr[i, j];
                }
            }

for (int i = 0; i < row; i++)
            {
                for (int j = 0; j < column; j++)
                {
                    if (result[i, j] == "C")
                    {
                        for (int a = 0; a < row; a++)
                        {
                            if (result[i, a] == "W")
                            {
                                result[i, a] = "C";
                            } 
                        }

for (int b = 0; b < column; b++)
                        {
                            if (result[b, j] == "W")
                            {
                                result[b, j] = "C";
                            }
                        }
                    }
                }
            }

return result;
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,17 sec, absolute running time: 0,11 sec, cpu time: 0,08 sec, average memory usage: 12 Mb, average nr of threads: 2, absolute service time: 0,33 sec