sort C# 2d array

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

namespace CS
{
    class Program
    {
        static void Main(string[] args)
        {
            int m = 5;
            int n = 6;
            int[,] a = new int[,]{
                {1, 4, 7, 2, 4, 3},
                {3, 2, 4, 6, 7, 1},
                {9, 2, 6, 1, 8, 3},
                {6, 2, 7, 9, 2, 5},
                {6, 8, 1, 6, 2, 5}
            };
            for (int i = 0; i < m; i++)
            {
                for (int j = 0; j < n; j++)
                {
                    for (int k = 0; k < m; k++)
                    {
                        for (int l = 0; l < n; l++)
                        {
                            if (a[i, j] < a[k, l])
                            {
                                int temp = a[i, j];
                                a[i, j] = a[k, l];
                                a[k, l] = temp;
                            }
                        }
                    }
                }
            }
        }
    }
}