用C#设计一个四则运算器

用C#设计一个四则运算器

 

 

 

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

namespace WindowsApplication21
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnequal_Click(object sender, EventArgs e)
        {
            string s1 = txt1.Text.Trim();
            string s2 = txt2.Text.Trim();

            int i1, i2,sum=0;
            if (int.TryParse(s1, out i1) == false)
            {
                MessageBox.Show("第一个输入的不是合法的字符");
                txt1.Focus();
                txt1.BackColor = Color.Blue;
                return;
            }
            else
            {
                txt1.BackColor = Color.White;
            }
            if (int.TryParse(s2, out i2) == false)
            {
                MessageBox.Show("第二个输入的不是合法的字符");
                txt2.Focus();
                txt2.BackColor = Color.Red;
            }
            else
            {
                txt1.BackColor = Color.White;
            }
           switch(comboBox1.SelectedIndex)
            {
               case 0:
                sum = i1 + i2;
                txt3.Text=sum.ToString();
                break;
               case 1:
                   sum = i1 - i2;
                  
                   break;
               case 2:
                   sum = i1 * i2;
                
                   break;
               case 3:
                   sum = i1 / i2;
               
                   break;
               case -1:
                   MessageBox.Show("你没有选择运算符");
                   break;
               default:
                   break;
                  
            }
            txt3.Text = sum.ToString();
        }

      
    }
}