.NET c#简单版计算机实现加减乘除

①在视图的工具箱中给form1窗口添加如下:

②combobox1的属性ltems赋值

并页面加载时设置combobox1无法编辑,只读;
③button1的text属性赋值"=";
④textbox3设置readonly属性,赋值true,让textbox3为只读;
⑤代码:

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

namespace _02计算器
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //分别获取textbox1,textbox2;combobox1的内容用变量接收
            int