按钮判断

书中代码
void Calc(object sender,EventArgs e)
{
double answer;
Button PressedButton=(Button)sender;
switch(PressedButton)
{
case "btnAdd":
    answer=Convert.ToDouble(tbxInput1.text)+Convert.ToDouble(tbxInput2.text);
    lblAnswer.Text=answer.ToString;
    break;
...........
但觉得判断哪个按钮按下,switch不是这样写法,请指教