加减乘除的数据存取访问

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;
using MySql.Data.MySqlClient;


namespace MySQLCalculate
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnCalculate_Click(object sender, EventArgs e)
        {
            int a, b, c;
            a = Convert.ToInt32(txtNum1.Text);
            b = Convert.ToInt32(txtNum2.Text);
            c = 0;

            string d = txtSign.Text;
            if (d == "+")
            {
                c = a + b;
            }
            if (d == "-")
            {
                c = a - b;
            }
            if (d == "*")
            {
                c = a * b;
            }
            if (d == "/")
            {
                c = a / b;
            }

            string strcn = "Server=127.0.0.1;User ID=root;Password=mysql;Database=test;CharSet=gbk;";
            MySqlConnection cn = new MySqlConnection(strcn);//实例化链接
            cn.Open();//开启连接

            MySqlCommand cmd = cn.CreateCommand();
            cmd.CommandText = "insert into Calculate(num1,sign,num2,outcome) values(‘" + a + "‘,‘" + d + "‘,‘" + b + "‘,‘" + c + "‘)";
            cmd.CommandType = CommandType.Text;
            int i = cmd.ExecuteNonQuery();
            
            cn.Close();//关闭连接
        }
    }
}