四则运算

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

namespace 四则运算
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public  int right = 0;//正确的题目个数
        public  int mistake =0;//错误的题目个数
        //随机产生的随机数0-10
        private void RandomNum()
        {
            Random ran = new Random();
            int n1, n2;
            n1 = ran.Next(0, 11);
            n2 = ran.Next(0, 11);
            textBox1.Text = n1.ToString();
            textBox2.Text = n2.ToString();
            textBox3.Text = "";
            
        }       
        public static int sum;
        //调换四则运算的方法
        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            
            textBox3.Focus();
            string str = comboBox1.SelectedItem.ToString(); 
            RandomNum();
            switch (str)
            {
                case "+":
                    sum = int.Parse(textBox1.Text) + int.Parse(textBox2.Text);
                    break;
                case "-":
                    sum = int.Parse(textBox1.Text) - int.Parse(textBox2.Text);
                    break;
                case "*":
                    sum = int.Parse(textBox1.Text) * int.Parse(textBox2.Text);
                    break;
                case "/":
                    sum = int.Parse(textBox1.Text) / int.Parse(textBox2.Text);
                    break;
            } 
           
        }
        
        //题目的正确个数的题目的错误个数
        private void button3_Click(object sender, EventArgs e)
        {
            textBox3.Focus();
            RandomNum();
            if(textBox3.Text == sum.ToString())
            {
                right++;
                RandomNum();
            }
            else
            {
                mistake++;
                RandomNum();
            }
            
        }
        private void button1_Click(object sender, EventArgs e)
        {
            textBox4.Text = right.ToString();
            textBox5.Text = mistake.ToString() ;
        }
    }
}
Psp分析: