//定義操作數(shù)和結(jié)果
string firstValue, secondValue, result;
char operation;
//存儲(chǔ)上次點(diǎn)擊了什么按鈕，0代表什么都沒(méi)點(diǎn)擊，1代表了數(shù)字按鈕
 private int lastButtonStatus = 0;

private void btnVaL_Click(object sender, EventArgs e)
 {
  Button btn = (Button)sender;
  if (lastButtonStatus == 0 || textBox_show.Text == "0")
  {
  textBox_show.Text = btn.Text;
  }
  else
  {
  textBox_show.Text += btn.Text;
  }
  lastButtonStatus = 1;
 }
 //將數(shù)字按鈕的事件集中處理
 private void Form1_Load(object sender, EventArgs e)
 {
  this.textBox_show.Text = "0";
  this.textBox_top.Text = "0";
  btn_0.Click += new EventHandler(btnVaL_Click);
  btn_1.Click += new EventHandler(btnVaL_Click);
  btn_2.Click += new EventHandler(btnVaL_Click);
  btn_3.Click += new EventHandler(btnVaL_Click);
  btn_4.Click += new EventHandler(btnVaL_Click);
  btn_5.Click += new EventHandler(btnVaL_Click);
  btn_6.Click += new EventHandler(btnVaL_Click);
  btn_7.Click += new EventHandler(btnVaL_Click);
  btn_8.Click += new EventHandler(btnVaL_Click);
  btn_9.Click += new EventHandler(btnVaL_Click);
  btn_point.Click += new EventHandler(btnVaL_Click);
 }

//加
 private void btn_add_Click(object sender, EventArgs e)
 {
  firstValue = textBox_show.Text;
  operation = '+';
  textBox_top.Text = firstValue + '+';
  textBox_show.Text = string.Empty;
 }
 //減
 private void btn_sub_Click(object sender, EventArgs e)
 {
  firstValue = textBox_show.Text;
  operation = '-';
  textBox_top.Text = firstValue + '-';
  textBox_show.Text = string.Empty;
 }
 //乘
 private void btn_mult_Click(object sender, EventArgs e)
 {
  firstValue = textBox_show.Text;
  operation = '*';
  textBox_top.Text = firstValue + '*';
  textBox_show.Text = string.Empty;
 }
 //除
 private void btn_div_Click(object sender, EventArgs e)
 {
  firstValue = textBox_show.Text;
  operation = '/';
  textBox_top.Text = firstValue + '/';
  textBox_show.Text = string.Empty;
 }
 //求余
 private void btn_remain_Click(object sender, EventArgs e)
 {
  firstValue = textBox_show.Text;
  operation = '%';
  textBox_top.Text = firstValue + '%';
  textBox_show.Text = string.Empty;
 }
 //求平方和
 private void btn_square_Click(object sender, EventArgs e)
 {
  firstValue = textBox_show.Text;
  textBox_top.Text = firstValue + "的平方是：";
  double outFirst;
  double.TryParse(firstValue, out outFirst);
  textBox_show.Text = (outFirst * outFirst).ToString();
 }
 //求平方根
 private void btn_involution_Click(object sender, EventArgs e)
 {
  firstValue = textBox_show.Text;
  textBox_top.Text = firstValue + "的平方根是：";
  double outFirst;
  double.TryParse(firstValue, out outFirst);
  textBox_show.Text = (Math.Sqrt(outFirst)).ToString();
 } 
 //等號(hào),處理加、減、乘、除、求余、運(yùn)算
 private void btn_equal_Click(object sender, EventArgs e)
 {
  secondValue = textBox_show.Text;
  textBox_top.Text += secondValue + '=';
  double outFirst, outSecond;
  double.TryParse(firstValue, out outFirst);
  double.TryParse(secondValue,out outSecond);
  switch (operation)
  {
  case '+':
   result = (outFirst + outSecond).ToString();
   break;
  case '-':
   result = (outFirst - outSecond).ToString();
   break;
  case '*':
   result = (outFirst * outSecond).ToString();
   break;
  case '/':
   if (outSecond != 0)
   {
   result = (outFirst / outSecond).ToString();
   }
   else
   {
   MessageBox.Show("被除數(shù)不能為0");
   }
   break;
  case '%':
   result = (outFirst % outSecond).ToString();
   break;
  }
  textBox_show.Text = result;
 }

//退格功能
 private void btn_back_Click(object sender, EventArgs e)
 {
  if (textBox_show.Text.Length > 0)
  {
  textBox_show.Text = textBox_show.Text.Substring(0, textBox_show.Text.Length - 1);
  }
 }
 //清空
 private void btn_clear_Click(object sender, EventArgs e)
 {
  textBox_top.Text = string.Empty;
  textBox_show.Text = string.Empty;
  firstValue = string.Empty;
  secondValue = string.Empty;
 }