Minúsculas a Mayusculas

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 numero17
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
//Variables

string textoentrada, textosalida;

private void button2_Click(object sender, EventArgs e)
{
Application.Exit();
}
//Entrada
private void textBox1_TextChanged(object sender, EventArgs e)
{
textoentrada = textBox1.Text;
}




//Proceso y salida
private void button1_Click(object sender, EventArgs e)
{
textosalida = textoentrada.ToUpper();
textBox2.Text = textosalida.ToString();
}
}
}