C#实现简单计算器功能

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 Cal
{
  public partial class Form1 : Form
  {
    public double num1;
    public int temp = 0;//记录存储计算方式
    public Form1()
    {
      InitializeComponent();
    }
    
    private void eq_Click(object sender, EventArgs e)
    {
      switch (temp)
      {
        //加法运算
        case 1:
          try
          {
            result.Text = (num1 + double.Parse(result.Text)).ToString();
          }
          catch (Exception)
          {
            MessageBox.Show("还没输入数字呢", "错误提示", MessageBoxButtons.OK, MessageBoxIcon.Warning);
          }
          finally
          {
            temp = 0;
          }
          break;
        //减法运算
        case 2:
          try
          {
            result.Text = (num1 - double.Parse(result.Text)).ToString();
          }
          catch (Exception)
          {
            MessageBox.Show("还没输入数字呢", "错误提示", MessageBoxButtons.OK, MessageBoxIcon.Warning);
          }
          finally
          {
            temp = 0;
          }
          break;
        //乘法运算
        case 3:
          try
          {
            result.Text = (num1 * double.Parse(result.Text)).ToString();
          }
          catch (Exception)
          {
            MessageBox.Show("还没输入数字呢", "错误提示", MessageBoxButtons.OK, MessageBoxIcon.Warning);
          }
          finally
          {
            temp = 0;
          }
          break;
        //除法运算，讨论分母为零的情况
        case 4:
          if (double.Parse(result.Text)==0)
          {
            MessageBox.Show("除数不能为零", "错误提示", MessageBoxButtons.OK, MessageBoxIcon.Warning);
            result.ResetText();
          }
          else
          {
            result.Text = (num1 / double.Parse(result.Text)).ToString(); temp = 0;
          }
          break;
        case 5:
          try
          {
            result.Text = (num1 % double.Parse(result.Text)).ToString();
          }
          catch (Exception)
          {
            MessageBox.Show("还没输入数字呢", "错误提示", MessageBoxButtons.OK, MessageBoxIcon.Warning);
          }
          finally
          {
            temp = 0;
          }
          break;
      }
    }

    private void empty_Click(object sender, EventArgs e)
    {
      result.Text = "0";
      num1 = 0;
      temp = 0;
      //清除
      //if (result.Text.Length > 0)
      //{
      //  result.Text = result.Text.Substring(0, result.Text.Length - 1);
      /