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

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

        private void button1_Click(object sender, EventArgs e)
        {
            int a, b, c, d;
            radioButton1.Enabled = true;
            radioButton2.Enabled = true;
            radioButton1.Checked = false;
            radioButton2.Checked = false;
            Random rnd = new Random();
            a = rnd.Next(99);
            b = rnd.Next(99);
            c = a + b;
            d = rnd.Next(c - 1, c + 1);
            textBox1.Text = Convert.ToString(a);
            textBox2.Text = Convert.ToString(b);
            textBox3.Text = Convert.ToString(d);
            button1.Enabled = false;
            radioButton1.Enabled = true;
            radioButton2.Enabled = true;
           label3.Text = "请选择";
             }

        private void radioButton1_CheckedChanged(object sender, EventArgs e)
        {
            int a, b, c, d;

            a = Convert.ToInt32(textBox1.Text);
            b = Convert.ToInt32(textBox2.Text);
            c = Convert.ToInt32(textBox3.Text);
            d = a + b;
            if (c == d)
            {
                label3.Text = "判断正确";
            }
            else
                label3.Text = "判断错误";
            radioButton1.Enabled = false;
            radioButton2.Enabled = false;
           button1.Enabled = true;

        }
         private void radioButton2_CheckedChanged(object sender, EventArgs e)
        {
            int a, b, c, d;

            a = Convert.ToInt32(textBox1.Text);
            b = Convert.ToInt32(textBox2.Text);
            c = Convert.ToInt32(textBox3.Text);
            d = a + b;
            if (c == d)
            {
                label3.Text = "判断错误";
            }
            else
                label3.Text = "判断正确";
            radioButton1.Enabled = false;
            radioButton2.Enabled = false;
            button1.Enabled = true;
    }
   }
  }


中间红色部分为什么要写两遍才能实现Butten和radiobutten两者的enable属性轮流在true和false之间切换！