C#实现的简单整数四则运算计算器功能示例

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
namespace 计算器
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
    }
    public　string　num;
    public int flag;//用于判断输入的操作符
    public double num1, num2;
    private void num0_button_Click(object sender, EventArgs e)
    {
      num = num + "0";
      num2 = Convert.ToDouble(num);
      textBox.Text = num;
    }
    private void num1_button_Click(object sender, EventArgs e)//重点算法1
    {
      if (textBox.Text == "0")
      {
        num = "1";
        textBox.Text = Convert.ToString(num);
      }
      else
      {
        num = num + "1";
        num2 = Convert.ToDouble(num);
        textBox.Text = num;
      }
    }
    private void num2_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text == "0")
      {
        num = "2";
        textBox.Text = Convert.ToString(num);
      }
      else
      {
        num = num + "2";
        num2 = Convert.ToDouble(num);
        textBox.Text = num;
      }
    }
    private void num3_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text == "0")
      {
        num = "3";
        textBox.Text = Convert.ToString(num);
      }
      else
      {
        num = num + "3";
        num2 = Convert.ToDouble(num);
        textBox.Text = num;
      }
    }
    private void num4_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text == "0")
      {
        num = "4";
        textBox.Text = Convert.ToString(num);
      }
      else
      {
        num = num + "4";
        num2 = Convert.ToDouble(num);
        textBox.Text = num;
      }
    }
    private void num5_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text == "0")
      {
        num = "5";
        textBox.Text = Convert.ToString(num);
      }
      else
      {
        num = num + "5";
        num2 = Convert.ToDouble(num);
        textBox.Text = num;
      }
    }
    private void num6_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text == "0")
      {
        num = "6";
        textBox.Text = Convert.ToString(num);
      }
      else
      {
        num = num + "6";
        num2 = Convert.ToDouble(num);
        textBox.Text = num;
      }
    }
    private void num7_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text == "0")
      {
        num = "7";
        textBox.Text = Convert.ToString(num);
      }
      else
      {
        num = num + "7";
        num2 = Convert.ToDouble(num);
        textBox.Text = num;
      }
    }
    private void num8_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text == "0")
      {
        num = "8";
        textBox.Text = Convert.ToString(num);
      }
      else
      {
        num = num + "8";
        num2 = Convert.ToDouble(num);
        textBox.Text = num;
      }
    }
    private void num9_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text == "0")
      {
        num = "9";
        textBox.Text = Convert.ToString(num);
      }
      else
      {
        num = num + "9";
        num2 = Convert.ToDouble(num);
        textBox.Text = num;
      }
    }
    private void add_button_Click(object sender, EventArgs e)//重点算法2
    {
      if (textBox.Text.Length > 0)
      {
        num1 = Convert.ToDouble(textBox .Text);
        num = "";
        flag = 1;
        textBox.Text = "";
        textBox.Focus();
      }
    }
    private void dev_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text.Length > 0)
      {
        num1 = Convert.ToDouble(textBox.Text);
        num = "";
        flag = 2;
        textBox.Text = "";
        textBox.Focus();
      }
    }
    private void mul_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text.Length > 0)
      {
        num1 = Convert.ToDouble(textBox.Text);
        num = "";
        flag = 3;
        textBox.Text = "";
        textBox.Focus();
      }
    }
    private void chu_button_Click(object sender, EventArgs e)
    {
      if (textBox.Text.Length > 0)
      {
        num1 = Convert.ToDouble(textBox.Text);
        num = "";
        flag = 4;
        // textBox.Text = "";
        textBox.Focus();
      }
    }
    private void equ_button_Click(object sender, EventArgs e)
    {
      switch (flag)
      {
        case 1:
          textBox.Text = Convert.ToString(num1+Convert .ToDouble(num));//重点算法3
          num2 = Convert.ToDouble(textBox .Text);
          break;
        case 2:
          textBox.Text = Convert.ToString(num1 - Convert.ToDouble(num));
          num2 = Convert.ToDouble(textBox.Text);
          break;
        case 3:
          textBox.Text = Convert.ToString(num1 * Convert.ToDouble(num));
          num2 = Convert.ToDouble(textBox.Text);
          break;
        case 4:
          textBox.Text = Convert.ToString(num1 / Convert.ToDouble(num));
          num2 = Convert.ToDouble(textBox.Text);
          break;
      }
    }
    private void re_button_Click(object sender, EventArgs e)
    {
      num = "";
      textBox.Text = "0";
    }
  }
}