Simple Calculator C#

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 hello
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

        }

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {

        }

        private void Form1_Load_1(object sender, EventArgs e)
        {


            comboBox1.Items.Add("+");
            comboBox1.Items.Add("-");
            comboBox1.Items.Add("*");
            comboBox1.Items.Add("/");
            Update();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            int val1 = int.Parse(textBox1.Text);
            int val2 = int.Parse(textBox2.Text);



            if (comboBox1.SelectedItem == "+")
            {
                textBox3.Text = (val1 + val2).ToString();
            }

            else if (comboBox1.SelectedItem == "-")
            {
                textBox3.Text = (val1 - val2).ToString();
            }

            else if (comboBox1.SelectedItem == "*")
            {
                textBox3.Text = (val1 * val2).ToString();
            }

            else if (comboBox1.SelectedItem == "/")
            {
                textBox3.Text = (val1 / val2).ToString();
            }

        }

        private void label5_Click(object sender, EventArgs e)
        {
            MessageBox.Show("Copyright (c) 2013 Touhid\n \nWebsite: www.touhid.info", "Copyright");
        }

    }
}