Calculadora em form

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 T2IT1_Exercicio0702
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button6_Click(object sender, EventArgs e)
        {
            Close();
        }

        private void button5_Click(object sender, EventArgs e)
        {
            textBox1.Clear();
            textBox2.Clear();
            textBox3.Clear();

            textBox1.Focus();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            int vA, vB, res;

            vA = int.Parse(textBox1.Text);
            vB = int.Parse(textBox2.Text);

            res = vA + vB;

            textBox3.Text = res.ToString();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            int vA, vB, res;

            vA = int.Parse(textBox1.Text);
            vB = int.Parse(textBox2.Text);

            res = vA - vB;

            textBox3.Text = res.ToString();
        }

        private void button3_Click(object sender, EventArgs e)
        {
            int vA, vB, res;

            vA = int.Parse(textBox1.Text);
            vB = int.Parse(textBox2.Text);

            res = vA * vB;

            textBox3.Text = res.ToString();
        }

        private void button4_Click(object sender, EventArgs e)
        {
            int vA, vB, res;

            vA = int.Parse(textBox1.Text);
            vB = int.Parse(textBox2.Text);

            res = vA / vB;

            textBox3.Text = res.ToString();
        }
    }
}