C# 小计算器

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 Calcu_Pro
{
    public partial class Calcu_form : Form
    {
        public Calcu_form()
        {
            InitializeComponent();
        }
        //运算数A 
        private string dblAcc;
        //运算数B
        private string dblSec;
        //通过获取strOper的值来决定运算+,-,*,/,=   
        private string strOper;
        // 这个成员变量用于标识是否进行过“=”运算,默认true为没有进行过此运算
        private bool equal_flag = true;
        //中间变量


        private string num = "";

        //获得结果button
        private void btn_equel_Click(object sender, EventArgs e)
        {
            if (equal_flag)
            {
                if ((!dblAcc.Equals("")) && (!dblSec.Equals("")) && (!strOper.Equals("")))
                {
                    txtResult.Text = "";
                    dblAcc = calculte(dblAcc, dblSec, strOper);
                    txtResult.Text = dblAcc;
                    // 点击过“=”后，标志位就变为false
                    equal_flag = false;
                }
                else
                {
                    MessageBox.Show("您的输入有误！", "提示");
                }
            }
            else
            {
                dblAcc = calculte(dblAcc, dblSec, strOper);
                txtResult.Text = dblAcc;
                equal_flag = false;
            }


        }
        //除法button
        private void btn_division_Click(object sender, EventArgs e)
        {
            num = "";
            //strOper = "/";
            operator_check(btn_division);
            
        }
        //乘法button
        private void btn_multiply_Click(object sender, EventArgs e)
        {
            num = "";
            //strOper = "*";
            operator_check(btn_multiply);
        }
        //减法button
        private void btn_subtract_Click(object sender, EventArgs e)
        {
            num = "";
            //strOper = "-";
            operator_check(btn_subtract);
        }
        //加法button
        private void btn_add_Click(object sender, EventArgs e)
        {
            num = "";
            //strOper = "+";
            operator_check(btn_add);

        }
        //数字1
        private void btn_one_Click(object sender, EventArgs e)
        {
            if (equal_flag)
            {
                numberInputCheck(btn_one);
            }
            else
            {
                numberInputCheck(btn_one);
                equal_flag = true;
            }

        }
        //数字2
        private void btn_two_Click(object sender, EventArgs e)
        {
            if (equal_flag)
            {
                numberInputCheck(btn_two);
            }
            else
            {
                numberInputCheck(btn_two);
                equal_flag = true;
            }
        }
        //数字3
        private void btn_three_Click(object sender, EventArgs e)
        {
            if (equal_flag)
            {
                numberInputCheck(btn_three);
            }
            else
            {
                numberInputCheck(btn_three);
                equal_flag = true;
            }
        }
        //数字4
        private void btn_four_Click(object sender, EventArgs e)
        {
            if (equal_flag)
            {
                numberInputCheck(btn_four);
            }
            else
            {
                numberInputCheck(btn_four);
                equal_flag = true;
            }
        }
        //数字5
        private void btn_five_Click(object sender, EventArgs e)
        {
            if (equal_flag)
            {
                numberInputCheck(btn_five);
            }
            else
            {
                numberInputCheck(btn_five);
                equal_flag = true;
            }
        }
        //数字6
        private void btn_six_Click(object sender, EventArgs e)
        {
            if (equal_flag)
            {
                numberInputCheck(btn_six);
            }
            else
            {
                numberInputCheck(btn_six);
                equal_flag = true;
            }
        }
        //数字7
        private void btn_seven_Click(object sender, EventArgs e)
        {
            if (equal_flag)
            {
                numberInputCheck(btn_seven);
            }
            else
            {
                numberInputCheck(btn_seven);
                equal_flag = true;
            }
        }
        //数字8
        private void btn_eight_Click(object sender, EventArgs e)
        {
            if (equal_flag)
            {
                numberInputCheck(btn_eight);
            }
            else
            {
                numberInputCheck(btn_eight);
                equal_flag = true;
            }
        }
        //数字9
        private void btn_nine_Click(object sender, EventArgs e)
        {
            if (equal_flag)
            {
                numberInputCheck(btn_nine);
            }
            else
            {
                numberInputCheck(btn_nine);
                equal_flag = true;
            }
        }
        //数字0
        private void btn_zero_Click(object sender, EventArgs e)
        {
            // 没有点击过等号
            if (equal_flag)
            {
                numberInputCheck(btn_zero);
            }
            else
            {
                numberInputCheck(btn_zero);
                equal_flag = true;
            }

        }

        private void button8_Click(object sender, EventArgs e)
        {
            txtResult.Text = "0.0";

        }
        
        private void numberInputCheck(Button button)
        {
            // 如果输入框中是“0.0”或者“0”，说明这个数字是第一个操作数           
            if (txtResult.Text.Equals("0.0") || txtResult.Text.Equals("0"))
            {
           
                txtResult.Text = button.Text;
                dblAcc =txtResult.Text;

            }
            // 如果输入框中不是上面的情况、长度不为0并且操作符已经输入，此时应该做的是第一个操作数拼接
            else if ((strOper == null) && (txtResult.Text.Length != 0) && (!txtResult.Text.Equals("0.0")) && (!txtResult.Text.Equals("0")))
            {
                txtResult.Text += button.Text;
                dblAcc =txtResult.Text;
          
            }
            // 如果输入框中不是上面的情况、长度不为0并且操作符已经输入，此时应该做的是第二个操作数拼接
            else if ((strOper!=null) && (txtResult.Text.Length != 0) && (!txtResult.Text.Equals("0.0")) && (!txtResult.Text.Equals("0")))
            {
                txtResult.Text = "";
                num += button.Text;
                txtResult.Text += num;
                dblSec = txtResult.Text;
             
            }
        }

        private void operator_check(Button button)
        {
            // 第二个操作数还没有输入，说明这是用户这个运算中的第一个操作符
            if ((dblAcc != null) && (dblSec==null))
            {
                strOper = button.Text;

            }
            // 两个操作数均不为空，说明这是第二个操作符了，这时应该将前两个运算数进行运算
            else if ((dblAcc!=null) && (dblSec!=null) && (strOper!=null) && equal_flag)
            {
                txtResult.Text = "";
                //当两个数都不为空的时候
                if (!dblAcc.Equals("") && !dblSec.Equals(""))
                {
                    dblAcc = calculte(dblAcc, dblSec, strOper);
                }
                txtResult.Text = dblAcc;
                num = "";
                dblSec = "";
            }
            // 完成前一个运算后直接点击运算符，此时应该将上一次的结果作为第二次运算的第一个操作数
            else if (!equal_flag)
            {
                strOper = button.Text;
                dblAcc =txtResult.Text;
                num = "";
            }
            // 直接点击操作符时提示出错！
            else if (dblAcc != null)
            {
                MessageBox.Show("请输入您要进行运算的数字！", "提示");
            }
            else
            {
                MessageBox.Show("wrong");
            }
            //前一个运算符
            strOper = button.Text;
        }

        private string calculte(string dblAcc, string dblSec, string strOper)
        {
            
                switch (strOper)
                {
                    case "+":
                        dblAcc = (double.Parse(dblAcc) + double.Parse(dblSec)).ToString();
                        return dblAcc;
                    case "-":
                        dblAcc = (double.Parse(dblAcc) - double.Parse(dblSec)).ToString();
                        return dblAcc;
                    case "*":
                        dblAcc = (double.Parse(dblAcc) * double.Parse(dblSec)).ToString();
                        return dblAcc;
                    case "/":
                        dblAcc = (double.Parse(dblAcc) / double.Parse(dblSec)).ToString();
                        return dblAcc;
                    default:
                        MessageBox.Show("您的操作有误！", "提示");
                        return "wrong";
                }
        }
        
    }
}