C# Print Diagonal matrix

Print diagonal matrix

using System;

namespace ConsoleApp1
{
    class Program
    {
        public static void Main(string[] args)
        {
            var matrix = new int[,] {
                { 1, 2, 3, 4,5},
                { 6, 7, 8, 9, 10},
                { 11, 12, 13, 14, 15},
                { 16, 17, 18, 19, 20}
            };

            var rows = matrix.GetLength(0);
            var columns = matrix.GetLength(1);

            var rowPointer = 0;

            Console.WriteLine("First half of the diagonal");

            //start from first row to last row 
            while (rowPointer < rows)
            {
                var i = rowPointer;
                var j = 0;

                //rows to column
                while (i >= 0)
                {
                    Console.Write(matrix[i, j]);
                    i--;
                    j++;
                }

                rowPointer++;
                Console.WriteLine();
            }


            var columnPointer = 1;

            Console.WriteLine("Second half of the diagonal");

            // number 1 column to all column
            while (columnPointer < columns)
            {
                var i = rows - 1;
                var j = columnPointer;

                //til last column and last row
                while (j <= columns - 1)
                {
                    Console.Write(matrix[i, j]);
                    i--;
                    j++;
                }
                columnPointer++;
                Console.WriteLine();
            }

            Console.Read();
        }
    }
}