Simple Calculator in C# window Application

Open Visual studio just follow to simple step

Visual c# - Windows From Application - OK
Take 3 text Boxes, 8 Buttons on Form 1 and Set button layout according to you

Now Copy This Code :

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

namespace My_calculator
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        Double i;

        private void button1_Click(object sender, EventArgs e)//double click on add Button
        {
            i = Convert.ToDouble(textBox1.Text);
            Double j = Convert.ToDouble(textBox2.Text);
            Double k = i + j;
            textBox3.Text = k.ToString();
        }

        private void button2_Click(object sender, EventArgs e)//double click on minus Button
        {
            i = Convert.ToDouble(textBox1.Text);
            Double j = Convert.ToDouble(textBox2.Text);
            Double k = i - j;
            textBox3.Text = k.ToString();
        }

        private void button3_Click(object sender, EventArgs e)//double click on multiply Button
        {
            i = Convert.ToDouble(textBox1.Text);
            Double j = Convert.ToDouble(textBox2.Text);
            Double k = i * j;
            textBox3.Text = k.ToString();
        }

        private void button4_Click(object sender, EventArgs e)//double click on divide Button
        {
            i = Convert.ToDouble(textBox1.Text);
            Double j = Convert.ToDouble(textBox2.Text);
            Double k = i / j;
            textBox3.Text = k.ToString();
        }

        private void button5_Click(object sender, EventArgs e)//double click on square root Button
        {
            i = Convert.ToDouble(textBox1.Text);
            //Double j = Convert.ToDouble(textBox2.Text);
            Double k = i * i;
            textBox3.Text = k.ToString();
        }

        private void button6_Click(object sender, EventArgs e)//double click on square cube  Button
        {
            i = Convert.ToDouble(textBox1.Text);
            //Double j = Convert.ToDouble(textBox2.Text);
            Double k = i * i * i;
            textBox3.Text = k.ToString();
        }

        private void button7_Click(object sender, EventArgs e)//double click on B(Blank) Button for clear text-boxes 
        {
            textBox1.Text = "";
            textBox2.Text = "";
            textBox3.Text = "";
        }

        private void button8_Click(object sender, EventArgs e)//double click on E(Exit) Button for closing application
        {
            Application.Exit();
        }
    }
}

now click F5 for run............. Your Suggestion in Comment Box