2D array to 1D List (2), 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)
        {
                      
            char[,] array = new char[6,4] { 
                { 'G', 'V', 'H', 'F' },
                { 'I', 'E', 'V', 'A' },
                { 'U', 'G', 'N', 'L' },
                { 'G', 'X', 'F', 'W' },
                { 'E', 'N', 'L', 'H' },
                { 'A', 'H', 'V', 'B' }
            };
            
            
            List<string> matrixCharacters = new List<string>();

for (int r = 0; r < array.GetLength(0); r++)
            {
                matrixCharacters.Add(string.Join("", Enumerable.Range(0, array.GetLength(1))
                                                               .Select(row => array[r, row])) + r.ToString());
            }
            
            
            // Display G0, V1, H2, F3, I4, E5, V6, A7, U8, G9, N10, L11...
            for (int c = 0; c < matrixCharacters.Count(); c++) 
            {  
                Console.WriteLine(string.Join("\n", matrixCharacters[c]));
            }
            
            
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,17 sec, absolute running time: 0,11 sec, cpu time: 0,09 sec, average memory usage: 12 Mb, average nr of threads: 2