计算器c语言

using System;
using System.Drawing;
using System.Windows;
using System.Windows.Forms;
using System.Collections;
using System.ComponentModel;
using System.Data;

namespace comput
{
  
    public class Form1 : System.Windows.Forms.Form
    {
        #region 控件声明
    
        private System.Windows.Forms.TextBox txtShow;
        private System.Windows.Forms.GroupBox groupBox1;
        private System.Windows.Forms.Button btn_rev;
        private System.Windows.Forms.Button btn_dot;
        private System.Windows.Forms.Button btn_add;
        private System.Windows.Forms.Button btn_equ;
        private System.Windows.Forms.Button btn_sign;
        private System.Windows.Forms.Button btn_sub;
        private System.Windows.Forms.Button btn_mul;
        private System.Windows.Forms.Button btn_0;
        private System.Windows.Forms.Button btn_3;
        private System.Windows.Forms.Button btn_2;
        private System.Windows.Forms.Button btn_1;
        private System.Windows.Forms.Button btn_6;

        private System.Windows.Forms.Button btn_5;
        private System.Windows.Forms.Button btn_4;
        private System.Windows.Forms.Button btn_sqrt;
        private System.Windows.Forms.Button btn_div;
        private System.Windows.Forms.Button btn_7;
        private System.Windows.Forms.Button btn_8;
        private System.Windows.Forms.Button btn_9;
        private System.Windows.Forms.MainMenu mainMenu1;
        private System.Windows.Forms.MenuItem menuItem1;
        private System.Windows.Forms.Button btn_sqr;
        private System.Windows.Forms.MenuItem menuItem2;
        private System.Windows.Forms.MenuItem menuItem3;
        private System.Windows.Forms.MenuItem menuItem4;
        private System.Windows.Forms.MenuItem menuItem5;
        private System.Windows.Forms.MenuItem menuItem6;
        private System.Windows.Forms.Button c;
        private System.Windows.Forms.Button ce;
        private System.Windows.Forms.MenuItem menuItem8;
        private System.Windows.Forms.MenuItem menuItem9;
        private System.Windows.Forms.MenuItem menuItem10;
        /// <summary>
        /// 必需的设计器变量。
        /// </summary>
        private System.ComponentModel.Container components = null;
        
        
        public Form1()
        {
            //
            // Windows 窗体设计器支持所必需的