igor

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

namespace igor
{
    class Matrix
    {
        private int[,] IntArray;
        private int n;

        public Matrix (int aN)
        {
            n = aN;
            IntArray = new int[n, n];
        }
        public void Input ()
        {
            for (int i = 0; i < n; i++)
            {
                for (int j = 0; j < n; j++)
                {
                    Console.Write("[{0},{1}] = ", i, j);
                    IntArray[i, j] = int.Parse(Console.ReadLine());
                }
            }
        }
        public void Print()
        {
            for (int i = 0; i < n; i++)
            {
                for (int j = 0; j < n; j++)
                {
                    Console.Write(IntArray[i, j]);
                }
                Console.WriteLine();
            }
        }
        public int ColSum(int col)
        {
            int sum = 0;
            for (int i = 0; i < n; i++)
            {
                sum += IntArray[i, col];
            }
            return sum;
        }
        public int NullCount
        {
            get {
                int count = 0;

                for (int i = 0; i < n; i++)
                    for (int j = 0; j < n; j++)
                        if(IntArray[i, j] == 0) count++;

                return count;
            }

        }
        public int MainDiagonal
        {
            set {
                for (int i = 0; i < n; i++)
                    IntArray[i, i] = value;
            }

        }

    }

    class Program
    {
        static void Main(string[] args)
        {
            Matrix matrix = new Matrix(3);
            matrix.Input();
            Console.WriteLine("set main diagonal to 9");
            matrix.MainDiagonal = 9;
            matrix.Print();
            Console.WriteLine("sum of 0 col = {0}", matrix.ColSum(0));
            Console.WriteLine("count of Null els = {0}", matrix.NullCount);
        }
    }


}