c# 四则运算自动出题器

界面

界面.PNG

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 WindowsFormsApp4
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {

        }

        int a, b;
        string op;
        int result;

        Random rnd = new Random();

        private void btnNew_Click(object sender, EventArgs e)
        {
            a = rnd.Next(9) + 1;
            b = rnd.Next(9) + 1;
            int c = rnd.Next(4);
            switch(c)
            {
                case 0:
                    op = "+";
                    result = a + b;
                    break;
                case 1:
                    op = "-";
                    result = a - b;
                    break;
                case 2:
                    op = "×";
                    result = a * b;
                    break;
                case 3:
                    op = "÷";
                    result = a / b;
                    break;
            }
            lblA.Text = a.ToString();
            lblB.Text = b.ToString();
            lblOp.Text = op;

            txtAnswer.Text = "";
        }



        private void btnJudge_Click(object sender, EventArgs e)
        {
            string str = txtAnswer.Text;
            double d = double.Parse(str);
            string disp = a + op + b +" = "+str;
            if (d == result) // if( Math.Abs(d-result)< 1e-3 )
                disp += " YES!";
            else
                disp += " NO!";
            lstDisp.Items.Add(disp);
        }
    }
}