Practica extra problema 1 visual

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 practica_extra_suma_de_nuemeros_visual

{

public partial class Form1 : Form

{

int n, suma, promedio, dato;

public Form1()

{

InitializeComponent();

n = suma = promedio = 0;

dato = 0;

label1.Text= "introduceun numero entero".ToString();

}

private void button1_Click(object sender, EventArgs e)

{

listBox1.Items.Add("numero entero");

n = int.Parse(textBox1.Text);

listBox1.Items.Add(n.ToString());

if (n != 9999)

{

suma = suma + n;

textBox1.Clear();

textBox1.Focus();

dato++;

if (n == 9999)

{

textBox1.Clear();

textBox1.Enabled = false;

button1.Enabled = false;

}

}

else

{

textBox1.Clear();

textBox1.Enabled = false;

button1.Enabled = false;

if (n == 0)

{

label1.Text = "introduceun numero diferente a 0".ToString();

}

}

}

private void button2_Click(object sender, EventArgs e)

{

promedio = suma / dato;

listBox1.Items.Add("el promedio es "+promedio.ToString());

}

private void button3_Click(object sender, EventArgs e)

{

listBox1.Items.Clear();

textBox1.Enabled = true;

button1.Enabled = true;

}

private void button4_Click(object sender, EventArgs e)

{

Close();

}

}

}