c# 小练习

double a = double.Parse( this.textBox1.Text);
double b = double.Parse(this.textBox2.Text);
double c =0;
switch (this.comboBox1.Text)
{
case "+":
c = a + b;
break;
case "-":
c = a - b;
break;
case "*":
c = a * b;
break;
case "/":
c = a / b;
break;

default:
c =0;
break;
}
MessageBox.Show(c.ToString());

double num1 = 0;
double num2 = 0;
if (!double.TryParse(this.textBox1.Text, out num1)) {

MessageBox.Show("s");
return;
}
if (!double.TryParse(this.textBox2.Text, out num2)) {

MessageBox.Show("s");
return;
}
this.label1.Text = (num1 + num2).ToString();