Sumar mediante una Función

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 numero13
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
//Variables
int n1, n2, s;
private void textBox1_TextChanged(object sender, EventArgs e)
{
n1 = int.Parse(textBox1.Text);
}

private void textBox2_TextChanged(object sender, EventArgs e)
{
n2 = int.Parse(textBox2.Text);
}

private void button1_Click(object sender, EventArgs e)
{
//Proceso
s = Sumar(n1, n2);
textBox3.Text = s.ToString();
}




//Metodo Sumar
private static int Sumar(int Num1, int Num2)
{
//Variables
int s;
// Proceso
s = Num1 + Num2;
//Salida
return s;
}

private void button2_Click(object sender, EventArgs e)
{
Application.Exit();
}

}
}