简易计算器

form后台具体代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Calculator
{
    public partial class Form1 : Form
    {
        private List<double> value_list = new List<double>();//存用户输入的数字
        private List<int> operator_list = new List<int>();//存用户输入的运算符，定义+为0，-为1，×为2，÷为3
        //状态记录
        private bool add_flag = false;//+按下
        private bool minus_flag = false;//-按下
        private bool multi_flag = false;//×按下
        private bool div_flag = false;//÷按下
        private bool result_flag = false;//=按下
        private bool can_operate_flag = false;//按下=是否响应

        public Form1()
        {
            InitializeComponent();
        }

        //数字键按下，含0与.，类似000001223这类情况这里允许，因为C#可以讲000001223自己转化为1223
        private void num_down(string num)
        {
            if (add_flag || minus_flag || multi_flag || div_flag || result_flag)
            {
                if (result_flag)//按下等号，刚刚算完一个运算的状态
                {
                    label1.Text = "";
                }
                textBox1.Clear();//如果用户刚刚输入完一个运算符
                add_flag = false;
                minus_flag = false;
                multi_flag = false;
                div_flag = false;
                result_flag = false;
            }
            if ((num.Equals(".") && textBox1.Text.IndexOf(".") < 0) || !num.Equals("."))
            {
                //如果用户输入的是小数点.，则要判断当前已输入的数字中是否含有小数点.才允许输入
                textBox1.Text += num;
                label1.Text += num;
                can_operate_flag = true;
            }
        }


        private void bt0_Click(object sender, EventArgs e)
        {
            num_down("0");
        }

        private void bt1_Click(object sender, EventArgs e)
        {
            num_down("1");
        }

        private void bt2_Click(object sender, EventArgs e)
        {
            num_down("2");
        }

        private void bt3_Click(object sender, EventArgs e)
        {
            num_down("3");
        }

        private void bt4_Click(object sender, EventArgs e)
        {
            num_down("4");
        }

        private void bt5_Click(object sender, EventArgs e)
        {
            num_down("5");
        }

        private void bt6_Click(object sender, EventArgs e)
        {
            num_down("6");
        }

        private void bt7_Click(object sender, EventArgs e)
        {
            num_down("7");
        }

        private void bt8_Click(object sender, EventArgs e)
        {
            num_down("8");
        }

        private void bt9_Click(object sender, EventArgs e)
        {
            num_down("9");
        }

        private void bt_point_Click(object sender, EventArgs e)
        {
            num_down(".");

        }

        //符号键的输入
        private void bt_plus_Click(object sender, EventArgs e)
        {
            if (!add_flag)//防止用户多次输入一个符号键，符号键只允许输入一次
            {
                result_flag = false;
                value_list.Add(double.Parse(textBox1.Text));//将当前已输入的数字放入value_list
                operator_list.Add(0);
                label1.Text += "+";
                add_flag = true;
                can_operate_flag = false;//刚刚输入完符号，不能构成一条正常的表达式，如111+，设置为不可运行状态
            }
        }

        private void bt_minus_Click(object sender, EventArgs e)
        {
            if (!minus_flag)
            {
                result_flag = false;
                value_list.Add(double.Parse(textBox1.Text));
                operator_list.Add(1);
                label1.Text += "-";
                minus_flag = true;
                can_operate_flag = false;
            }
        }

        private void bt_multi_Click(object sender, EventArgs e)
        {
            if (!multi_flag)
            {
                result_flag = false;
                value_list.Add(double.Parse(textBox1.Text));
                operator_list.Add(2);
                label1.Text = "(" + label1.Text + ")" + "×";//给前面的已经输入的东西加个括号。（运算符栈问题是一个很复杂的数据结构问题，这里不做，：P）
                multi_flag = true;
                can_operate_flag = false;
            }
        }

        private void bt_div_Click(object sender, EventArgs e)
        {
            if (!div_flag)
            {
                result_flag = false;
                value_list.Add(double.Parse(textBox1.Text));
                operator_list.Add(3);
                label1.Text = "(" + label1.Text + ")" + "÷";
                div_flag = true;
                can_operate_flag = false;
            }
        }

        private void bt_result_Click(object sender, EventArgs e)
        {

            if (value_list.Count > 0 && operator_list.Count > 0 && can_operate_flag)
            {//需要防止用户没输入数字，或者只输入了一个数，就按=。
                value_list.Add(double.Parse(textBox1.Text));
                double total = value_list[0];
                for (int i = 0; i < operator_list.Count; i++)
                {
                    int _operator = operator_list[i];//operator是C#的运算符重载的关键字，前面加个_来区别
                    switch (_operator)
                    {
                        case 0:
                            total += value_list[i + 1];
                            break;
                        case 1:
                            total -= value_list[i + 1];
                            break;
                        case 2:
                            total *= value_list[i + 1];
                            break;
                        case 3:
                            total /= value_list[i + 1];
                            break;
                    }
                }
                textBox1.Text = total + "";
                label1.Text = total + "";
                operator_list.Clear();//算完，就清空累积数字与运算数组
                value_list.Clear();
                result_flag = true;//表示=按下
            }
        }

        //CE键，将所有东西初始化
        private void btCE_Click(object sender, EventArgs e)
        {
            operator_list.Clear();
            value_list.Clear();
            add_flag = false;
            minus_flag = false;
            multi_flag = false;
            div_flag = false;
            result_flag = false;
            can_operate_flag = false;
            textBox1.Clear();
            label1.Text = "";
        }

    }
}