---

private void buttonCalculate_Click(object sender, EventArgs e)
{
    double value1 = (double)numericUpDown1.Value;
    double value2 = (double)numericUpDown2.Value;
    double value3 = (double)numericUpDown3.Value;

    double result = 0;

    if (comboBoxFigure.SelectedIndex == 0)
    {
        result = GeometryHelper.CalculateArea(value1);
    }
    else if (comboBoxFigure.SelectedIndex == 1)
    {
        result = GeometryHelper.CalculateArea(value1, value2);
    }
    else if (comboBoxFigure.SelectedIndex == 2)
    {
        result = GeometryHelper.CalculateArea(value1, true);
    }
    else if (comboBoxFigure.SelectedIndex == 3)
    {
        result = GeometryHelper.CalculateArea(value1, value2, value3);
    }
    else if (comboBoxFigure.SelectedIndex == 4)
    {
        result = GeometryHelper.CalculateArea(value1, value2, value3, true);
    }

    labelResult.Text = "Площадь: " + result.ToString("0.00");
}