C# Program to perform Addition,Subtraction,Multiplication & Division in single application

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 add

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        //for addition

        private void button1_Click_1(object sender, EventArgs e)

        {

            Double a, b, c;

            a = Convert.ToDouble(textBox1.Text);

            b = Convert.ToDouble(textBox2.Text);

            c = a + b;

            label3.Text = Convert.ToString(c);

            label3.Show();

            label4.Show();

           

        }

        //for subtraction

        private void button2_Click(object sender, EventArgs e)

        {

            Double a, b, c;

            a = Convert.ToDouble(textBox1.Text);

            b = Convert.ToDouble(textBox2.Text);

            c = a - b;

            label3.Text = Convert.ToString(c);

            label3.Show();

            label4.Show();

           

        }

        //for multiplication

        private void button3_Click(object sender, EventArgs e)

        {

            Double a, b, c;

            a = Convert.ToDouble(textBox1.Text);

            b = Convert.ToDouble(textBox2.Text);

            c = a * b;

            label3.Text = Convert.ToString(c);

            label3.Show();

            label4.Show();

        }

        //for division

        private void button4_Click(object sender, EventArgs e)

        {

            Double a, b, c;

            a = Convert.ToDouble(textBox1.Text);

            b = Convert.ToDouble(textBox2.Text);

            c = a / b;

            label3.Text = Convert.ToString(c);

            label3.Show();

            label4.Show();

        }

        //use only for valid input (eg-not taking character only numbers and dot) 

        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)

        {

            if (!((e.KeyChar >= 48 && e.KeyChar <= 57) || e.KeyChar == 46 || e.KeyChar == 8 || e.KeyChar == 9))

                e.Handled = true;

        }

        private void textBox2_KeyPress(object sender, KeyPressEventArgs e)

        {

            if (!((e.KeyChar >= 48 && e.KeyChar <= 57) || e.KeyChar == 46 || e.KeyChar == 8 || e.KeyChar == 9))

                e.Handled = true;

        }

   

    }

}

                                                    Output