Fill the Matrix

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

namespace MultiDimensionalArrays
{
    class Program
    {
        static void Main(string[] args)
        {
            int inputNum = int.Parse(Console.ReadLine());
            string inputChar = Console.ReadLine();

            int[,] array = new int[inputNum, inputNum];

            switch (inputChar)
            {
                case "a": VerticalMatrix(array, inputNum); break;
                case "b": HorizontalMatrix(array, inputNum); break;
                case "c": DiagonalMatrix(array, inputNum); break;
                case "d": break;
                default: Console.WriteLine("Invalid input!"); break;
            }
            PrintMatrix(inputNum, array);

        }
        public static void VerticalMatrix(int[,] array, int num)
            {

            int counter = 1;
            for (int cols = 0; cols < num; cols++)
            {
                for (int rows = 0; rows < num; rows++)
                {
                    array[rows, cols] = counter;

                    counter++;
                }
            }
            }

        public static void HorizontalMatrix(int[,] array, int num)
        {
            int counter = 1;

            for (int cols = 0; cols < num; cols++)
            {
                if (cols % 2 == 0)
                {
                    for (int rows = 0; rows < num; rows++)
                    {
                        array[rows, cols] = counter;
                        counter++;
                    }
                }
                else
                {
                    for (int rows = num - 1; rows >= 0; rows--)
                    {
                        array[rows, cols] = counter;
                        counter++;
                    }
                }
            }
        }
        public static void DiagonalMatrix(int[,] array, int num)
        {
            int counter = 1;
            int rows = 0;
            int cols = 0;
            int currentElements = 1;

            //first part very good
            for (int diagonal = num - 1; diagonal > 0; diagonal--)
            {
                rows = diagonal;
                cols = 0;
                for (int elements = 0; elements < currentElements; elements++)
                {
                    array[rows, cols] = counter;
                    counter++;
                    rows++;
                    cols++;
                }
                currentElements++;
            }
            //second part i no like
            for (int diagonal = 0; diagonal < num; diagonal++)
            {
                rows = 0;
                cols = diagonal;
                for (int elements = 0; elements < currentElements; elements++)
                {
                    array[rows, cols] = counter;
                    counter++;
                    rows++;
                    cols++;
                }
                currentElements--;
            }
        }

        public static void PrintMatrix(int num, int[,] array)
        {
            for (int rows = 0; rows < num; rows++)
            {
                for (int cols = 0; cols < num; cols++)
                {
                    if (cols == num - 1)
                    {
                        Console.Write("{0}", array[rows, cols]);
                    }
                    else
                    {
                        Console.Write("{0} ", array[rows,cols]);
                    }
                }
                Console.WriteLine();
            }
        }
    }
}