2DArray Sums

using System;

namespace P61Ex3
{
    class Program
    {
        public static int OverMainDiagonalSum(int[,] a)
        {
            int sum = 0;
            for (int i = 0; i < a.GetLength(0); i++)
            {
                for (int k = i + 1; k < a.GetLength(1); k++)
                    sum += a[i, k];
            }
            return sum;
        }
        public static int UnderMainDiagonalSum(int[,] a)
        {
            int sum = 0;
            for (int i = 0; i < a.GetLength(0); i++)
            {
                for (int k = 0; k < i; k++)
                    sum += a[i, k];
            }
            return sum;
        }
        public static int OverSecondaryDiagonalSum(int[,] a)
        {
            int sum = 0;
            for (int i = 0; i < a.GetLength(0); i++)
            {
                for (int k = 0; k < a.GetLength(1) - i - 1; k++)
                    sum += a[i, k];
            }
            return sum;
        }
        public static int UnderSecondaryDiagonalSum(int[,] a)
        {
            int sum = 0;
            for (int i = 0; i < a.GetLength(0); i++)
            {
                for (int k = 0; k < i; k++)
                    sum += a[i, a.GetLength(1) - k - 1];
            }
            return sum;
        }
        public static int FrameSum(int[,] a)
        {
            int sum = 0;
            for (int i = 0; i < a.GetLength(0); i++)
            {
                if (i == 0 || i == a.GetLength(0) - 1)
                    for (int k = 0; k < a.GetLength(1); k++)
                        sum += a[i, k];
                else
                    sum += a[i, 0] + a[i, a.GetLength(1) - 1];
            }
            return sum;
        }
        public static string RowSum(int[,] a)
        {
            int sum = 0;
            string sumStr = "";
            for (int i = 0; i < a.GetLength(0); i++)
            {
                sum = 0;
                sumStr += "Row " + (i + 1);
                for (int k = 0; k < a.GetLength(1); k++)
                {
                    sum += a[i, k];
                }
                sumStr += " sum " + sum + " --- ";
            }
            return sumStr;
        }
        public static string ColumnSum(int[,] a)
        {
            int sum = 0;
            string sumStr = "";
            for (int i = 0; i < a.GetLength(1); i++)
            {
                sum = 0;
                sumStr += "Column " + (i + 1);
                for (int k = 0; k < a.GetLength(0); k++)
                {
                    sum += a[k, i];
                }
                sumStr += " sum " + sum + " --- ";
            }
            return sumStr;
        }
        public static int MainDiagonalSum(int[,] a)
        {
            int sum = 0;
            for (int i = 0; i < a.GetLength(0); i++)
                sum += a[i, i];
            return sum;
        }
        public static int SecondaryDiagonalSum(int[,] a)
        {
            int sum = 0;
            for (int i = 0; i < a.GetLength(0); i++)
                sum += a[i, a.GetLength(1) - i - 1];
            return sum;
        }
        static void Main()
        {
            int[,] arr = new int[5, 5];
            Random rnd = new Random();
            for (int i = 0; i < arr.GetLength(0); i++)
            {
                for (int k = 0; k < arr.GetLength(1); k++)
                    arr[i, k] = rnd.Next(1, 10);
            }
            for (int i = 0; i < arr.GetLength(0); i++)
            {
                for (int k = 0; k < arr.GetLength(1); k++)
                    Console.Write(arr[i, k] + " ");
                Console.WriteLine();
            }
            Console.WriteLine();
            Console.WriteLine("Row sums\n" +RowSum(arr));
            Console.WriteLine("Column sums\n" + ColumnSum(arr));
            Console.WriteLine("Frame sum " + FrameSum(arr));
            Console.WriteLine("Main diagonal sum " + MainDiagonalSum(arr));
            Console.WriteLine("Over main diagonal sum " + OverMainDiagonalSum(arr));
            Console.WriteLine("Under main diagonal sum " + UnderMainDiagonalSum(arr));
            Console.WriteLine("Seocndary diagonal sum " + SecondaryDiagonalSum(arr));
            Console.WriteLine("Over secondary diagonal sum " + OverSecondaryDiagonalSum(arr));
            Console.WriteLine("Under secondary diagonal sum " + UnderSecondaryDiagonalSum(arr));
        }
    }
}