zadanie 3 programowanie

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace My_DataGridView
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Int16 M, N;
            double Sum;
            M = Convert.ToInt16(numericUpDown1.Value);
            N = Convert.ToInt16(numericUpDown2.Value);
            Sum = 0;
            for (int i = 0; i < M; i++)
                for (int j = 0; j < N; j++)
                {
                    Sum = Sum + Convert.ToDouble(dataGridView1.Rows[i].Cells[j].Value);
                }
            textBox1.Text = Convert.ToString(Sum);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Int16 M, N;
            M = Convert.ToInt16(numericUpDown1.Value);
            N = Convert.ToInt16(numericUpDown2.Value);
            for (int i = 0; i < M; i++)
                for (int j = 0; j < N; j++)
                {
                   dataGridView1.Rows[i].Cells[j].Value=" ";
                }
            textBox1.Text =" ";
        }
    }
}