Kronometre ( Stopwatch ) - Csharp

int a;
private void button1_Click(object sender, EventArgs e)
{
timer1.Start();

}

private void timer1_Tick(object sender, EventArgs e)
{

if (int.Parse(label8.Text) < 9)
{
label8.Text = "0" + (int.Parse(label8.Text) + 1).ToString();
}
else {
label8.Text = (int.Parse(label8.Text) + 1).ToString();
}
if (int.Parse(label8.Text) == 60)
{
label8.Text = "00";
if (int.Parse(label6.Text) < 9)
{
label6.Text = "0" + (int.Parse(label6.Text) + 1).ToString();
}
else
{
label6.Text = (int.Parse(label6.Text) + 1).ToString();
}
}
if (int.Parse(label6.Text) == 60)
{
label6.Text = "00";
if (int.Parse(label4.Text) < 9)
{
label4.Text = "0" + (int.Parse(label4.Text) + 1).ToString();
}
else
{
label4.Text = (int.Parse(label4.Text) + 1).ToString();
}
}

}

private void button3_Click(object sender, EventArgs e)
{
timer1.Stop();
}

private void button4_Click(object sender, EventArgs e)
{
label4.Text = "00";
label6.Text = "00";
label8.Text = "00";
listBox1.Items.Clear();
}

private void button2_Click(object sender, EventArgs e)
{
listBox1.Items.Add(label4.Text + " " + label6.Text + " " + label8.Text);
}