Addition in c sharp for beginner

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

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void textBox3_TextChanged(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            int i1, i2, sum;

            i1 = Convert.ToInt16(texInp1.Text);
            i2 = Convert.ToInt16(texInp2.Text);

            sum = i1 + i2;
            texInp3.Text = Convert.ToString(sum);
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }
    }
}