aplicacion que usa pilas con listas

class Elemento
{
public int v;
public Elemento s;
public Elemento(int v1, Elemento s1)
{
v = v1;
s = s1;
}
}
class ExaU3
{
Elemento e1;
public ExaU3()
{
e1 = null;
}
public void metodo1(int v1)
{
Elemento nuevo = new Elemento(v1, e1);
e1 = nuevo;

}
public int metodo2()
{
Elemento naux;
int v1;
if (e1 == null)
return -1;
naux = e1;
e1 = naux.s;
v1 = naux.v;
return v1;
}
}

Main:
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 Tarea_PilaListas
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
ExaU3 examen = new ExaU3();
private void Form1_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
examen.metodo1(Convert.ToInt32(textBox1.Text));
//MessageBox.Show("Agregado " + textBox1.Text);

}
private void button2_Click(object sender, EventArgs e)
{
label2.Text = examen.metodo2().ToString();
}
}
}