用随机数， 设计一个100以内的加减乘除测试器， 数字，运算均随机产生。并根据计算的结果给出分数。（GUI界面）
数字和具体进行什么运算可以都利用随机数处理。必须使用方法。个人设计界面

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

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Random radnom = new Random();
            textBox1.Text = radnom.Next(101).ToString();
            textBox3.Text = radnom.Next(101).ToString();
            decimal result;
            switch (radnom.Next(4).ToString())
            {
                case "0":
                    textBox2.Text = "加";
                    result = Decimal.Round((Decimal.Parse(textBox1.Text.ToString()) + Decimal.Parse(textBox3.Text.ToString())),4);
                    textBox4.Text =result.ToString();
                    break ;
                case "1":
                    textBox2.Text = "减";
                    result = Decimal.Round((Decimal.Parse(textBox1.Text.ToString()) -Decimal.Parse(textBox3.Text.ToString())), 4);
                    textBox4.Text = result.ToString();
                    break;
                case "2":
                    textBox2.Text = "乘";
                    result = Decimal.Round((Decimal.Parse(textBox1.Text.ToString()) *Decimal.Parse(textBox3.Text.ToString())), 4);
                    textBox4.Text = result.ToString();
                    break;
                case "3":
                    textBox2.Text = "除";
                    result = Decimal.Round((Decimal.Parse(textBox1.Text.ToString()) /Decimal.Parse(textBox3.Text.ToString())), 4);
                    textBox4.Text = result.ToString();
                    break;
                default :               
                    break ;
            }

        }
    }
}