Pokračování:
private void button4_Click(object sender, EventArgs e)
{
clear = Clear(clear);
if (label1.Text.Length < 28)
label1.Text = label1.Text + "2";
else SystemSounds.Beep.Play();
}

private void button3_Click(object sender, EventArgs e)
{
clear = Clear(clear);
if (label1.Text.Length < 28)
label1.Text = label1.Text + "3";
else SystemSounds.Beep.Play();
}

private void button8_Click(object sender, EventArgs e)
{
clear = Clear(clear);
if (label1.Text.Length < 28)
label1.Text = label1.Text + "4";
else SystemSounds.Beep.Play();
}

private void button7_Click(object sender, EventArgs e)
{
clear = Clear(clear);
if (label1.Text.Length < 28)
label1.Text = label1.Text + "5";
else SystemSounds.Beep.Play();
}

private void button6_Click(object sender, EventArgs e)
{
clear = Clear(clear);
if (label1.Text.Length < 28)
label1.Text = label1.Text + "6";
else SystemSounds.Beep.Play();
}

private void button1_Click(object sender, EventArgs e)
{
clear = Clear(clear);
if (label1.Text.Length < 28)
label1.Text = label1.Text + "7";
else SystemSounds.Beep.Play();
}

private void button10_Click(object sender, EventArgs e)
{
clear = Clear(clear);
if (label1.Text.Length < 28)
label1.Text = label1.Text + "8";
else SystemSounds.Beep.Play();
}

private void button9_Click(object sender, EventArgs e)
{
clear = Clear(clear);
if (label1.Text.Length < 28)
label1.Text = label1.Text + "9";
else SystemSounds.Beep.Play();
}

private void button13_Click(object sender, EventArgs e)
{
if (label1.Text.Contains(','))
{
SystemSounds.Beep.Play();
}
else label1.Text = label1.Text + ",";
}

private void button11_Click(object sender, EventArgs e)
{
if (clear == 3 || clear == 4 || clear == 5)
label2.Text = label2.Text + " + ";
else label2.Text = label2.Text + label1.Text + " + ";
label1.Text = eval(op).ToString();
op = "+";
}

private void button14_Click(object sender, EventArgs e)
{
if (clear == 3 || clear == 4 || clear == 5)
label2.Text = label2.Text + " - ";
else label2.Text = label2.Text + label1.Text + " - ";
label1.Text = eval(op).ToString();
op = "-";
}

private void button15_Click(object sender, EventArgs e)
{
if (clear == 3 || clear == 4 || clear == 5)
label2.Text = label2.Text + " * ";
else label2.Text = label2.Text + label1.Text + " * ";
label1.Text = eval(op).ToString();
op = "*";
}