//Subtraction event
private void rbSub_Click(object sender, EventArgs e)
{
isValid(); //验证
if (isException)
{
complex = complexNumber1 - complexNumber2; //调用重载后的 - 运算
tbResult.Text = $"减法运算：{complexNumber1.ToString()}-({complexNumber2.ToString()})" +
$"={complex.ToString()}";
}
}
//Addition event
private void rbAdd_Click(object sender, EventArgs e)
{
isValid(); //验证
if (isException)
{
complex = complexNumber1 + complexNumber2; //调用重载后的 + 运算
tbResult.Text = $"加法运算：{complexNumber1.ToString()}+" +
$"{(complexNumber2.A < 0 ? "(" + complexNumber2.ToString() + ")" : complexNumber2.ToString())}" +
$"={complex.ToString()}"; //中间的三目运算表达式表示当第二个复数的实部为负时，加括号
}
}