用类做封装

form1

namespace 数学测试
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        Class1 fengzhuang = new Class1();//调用封装的内容
        string lujing = "D:	xt";
        public static int Count = 0; // 题目出的数量
        public static int cuo = 0; 
        public static int dui = 0;
        public static int jishi;
        public static int time;
        public static int sum;
        int i = 0;

        private void textBox9_TextChanged(object sender, EventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)//打开文件
        {
            OpenFileDialog baocun = new OpenFileDialog();
            baocun.Filter = "TXT文件(*.txt)|*.txt";
            if (baocun.ShowDialog() == DialogResult.OK)
            {
                lujing = baocun.FileName;
                this.richTextBox1.LoadFile(baocun.FileName, RichTextBoxStreamType.RichText);
                daikai.Enabled = false;
                save.Enabled = false;
                MessageBox.Show("读取成功", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);

            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Count++;
            StreamWriter xie = File.AppendText("xie.txt");
            xie.WriteLine(t1.Text);
            xie.Close();
            StreamWriter xie1 = File.AppendText("xie1.txt");
            xie1.WriteLine(t2.Text);
            xie1.Close();
            StreamWriter xie2 = File.AppendText("xie2.txt");
            xie2.WriteLine(t3.Text);
            xie2.Close();

            richTextBox1.Text += t1.Text + t2.Text + t3.Text + label1.Text + "
";
            t1.Clear();
            t2.Clear();
            t3.Clear();



        }

        private void richTextBox1_TextChanged(object sender, EventArgs e)
        {
            save.Enabled = true;
            if (this.richTextBox1.Text == "" || this.richTextBox1.Text == null)
            {
                daikai.Enabled = true;
            }
        }

        private void save_Click(object sender, EventArgs e)//保存文件
        {
            SaveFileDialog baocun = new SaveFileDialog();
            baocun.Filter = "TXT文件(*.txt)|*.txt";
            if (File.Exists(lujing))
            {
                this.richTextBox1.LoadFile(lujing, RichTextBoxStreamType.RichText);
                MessageBox.Show("保存成功", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
                this.richTextBox1.Clear();
                save.Enabled = false;
            }
            else
            {
                if (baocun.ShowDialog() == DialogResult.OK)
                {
                    this.richTextBox1.SaveFile(baocun.FileName, RichTextBoxStreamType.RichText);
                    MessageBox.Show("保存成功", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
                    this.richTextBox1.Clear();
                    save.Enabled = false;
                }
            }

        }

        private void kaishi_Click(object sender, EventArgs e)
        {
           
            string[] T1 = new string[100];
            T1 = File.ReadAllLines("xie.txt");
            tB1.Text = T1[0];
            string[] T2 = new string[100];

            T2 = File.ReadAllLines("xie1.txt");
            tB2.Text = T2[0];
            string[] T3 = new string[100];

            T3 = File.ReadAllLines("xie2.txt");
            tB3.Text = T3[0];
            int daojishi;
            try
            {
                daojishi = int.Parse(this.shijian.Text);
            }
            catch (Exception ex)
            {

                MessageBox.Show("输入错误");
                return;
            }
            jishi = daojishi;
            this.timer1.Interval = 1000;
            this.timer1.Enabled = true;
            this.timer1.Start();
         
            
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            time = Convert.ToInt32(shijian.Text);
            if (jishi <= 0)
            {
                timer1.Enabled = false;
                MessageBox.Show("答题时间到！");
                daan.Enabled = false;
                Form2 frm2 = new Form2();
                frm2.ShowDialog();

            }
            this.label3.Text = "剩余时间" + jishi.ToString() + "秒";
            jishi--;
        }

        private void daan_KeyDown(object sender, KeyEventArgs e)
        {
          
            fengzhuang.a = (int.Parse(tB1.Text));
            fengzhuang.b = (int.Parse(tB3.Text));
            Class1.fh = tB2.Text;
            fengzhuang.jisuan();
            int result;

            if (e.KeyCode == Keys.Enter)
            {
                if (int.TryParse(daan.Text, out result) == false)
                {
                    MessageBox.Show("请输入数字");
                }
                daan.Text += sum ;
                if (daan.Text == fengzhuang.sum.ToString())
                {
                    MessageBox.Show("回答正确");
                    Count++;
                    dui++;
                }
                else
                {
                  
                    cuo++;
                }
                i++;
                daan.Clear();
                string[] T1 = new string[100];
                T1 = File.ReadAllLines("xie.txt");
                tB1.Text = T1[i];
                string[] T2 = new string[100];

                T2 = File.ReadAllLines("xie1.txt");
                tB2.Text = T2[i];
                string[] T3 = new string[100];

                T3 = File.ReadAllLines("xie2.txt");
                tB3.Text = T3[i];
                
            }
        }

        private void dakaishiti_Click(object sender, EventArgs e)
        {
            OpenFileDialog dakai = new OpenFileDialog();
            dakai.Filter = "TXT文件(*.txt)|*.txt";
            if (dakai.ShowDialog() == DialogResult.OK)
            {
                lujing = dakai.FileName;
                this.richTextBox2.LoadFile(dakai.FileName, RichTextBoxStreamType.RichText);
                save.Enabled = false;
                kaishi.Enabled = false;
                MessageBox.Show("打开成功", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
            }
        }

        private void daorushiti_Click(object sender, EventArgs e)
        {
            richTextBox2.Text = richTextBox1.Text;
        }

        private void jieshu_Click(object sender, EventArgs e)
        {
            daan.Enabled = false;
            Form2 frm2 = new Form2();
            frm2.ShowDialog();
           
        }
    }
}

form2

namespace 数学测试
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void Form2_Load(object sender, EventArgs e)
        {
            textBox2.Text = Form1.dui.ToString();
            textBox1.Text = Form1.Count.ToString();
            textBox3.Text = ((Form1.Count - (double)(Form1.dui))).ToString();
            textBox4.Text = ((Form1.dui / (double)(Form1.cuo)) * 100).ToString("f2") + "%";
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Class1 fengzhuang = new Class1();
            Application.Exit();
            fengzhuang.chongzhi();
        }
    }
}

类的封装

namespace 数学测试
{
    class Class1
    {

        public int a, b; 
        public int sum;
        public static string fh;
        public void chongzhi() //重新输入新的内容
        {
            File.WriteAllText("writer.txt", string.Empty);
            File.WriteAllText("writer1.txt", string.Empty);
            File.WriteAllText("xie.txt", string.Empty);
            File.WriteAllText("xie1.txt", string.Empty);
            File.WriteAllText("xie2.txt", string.Empty);
        }
         public void jisuan()  //计算方法
        {
            
            switch (fh)
            {
                case "+":
                    sum = a + b ;
                    break;
                case "-":
                    sum = a - b ;
                    break;
                case "*":
                    sum = a*b;
                    break;
                case"/":
                    sum = a / b;
                    break;
                default:
                    break;
            }
        }
    }
}

程序调试