计算器软件的代码实现 （策略模式）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace shuxuefudao
{
    class qita
    {

        public void qingkong()
        {
            File.WriteAllText("writer.txt", string.Empty);
            File.WriteAllText("writer1.txt", string.Empty);
            File.WriteAllText("writer2.txt", string.Empty);
        }
    }
    public interface Calculator //声明一个计算的接口
    {
        double Cal(double a,double  b);
    }
   public class Add : Calculator   //接口实现加法运算
   {
     public double Cal(double a, double b)
     {
         double result = 0;
         result = a + b;
         return result;
     }
   }
   public class Sub : Calculator //接口实现减法运算
 {
     public double Cal(double a, double b)
     {
         double result = 0;
         result = a - b;
         return result;
     }
 }
   public class Mul : Calculator  //接口实现乘法运算
 {
     public double Cal(double a, double b)
     {
         double result = 0;
         result = a * b;
        return result;
    }
 }
   public class Div : Calculator  //接口实现除法运算
 {
    public  double Cal(double a, double b)
    {
        double result = 0;
        result = a / b;
        return result;
     }
 }
 public class  Environment        //定义那个需要动态改变算法的对象   
 {
     private Calculator calculate;
     public Environment(Calculator calculate)
     {
        this.calculate = calculate;    
     }
     public double Cal(double a, double b, String m) //返回运算结果
     {
         return this.calculate.Cal(a, b);
    }
 }
 }
 

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;
using System.IO;

namespace shuxuefudao
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        string path = "E:\rtf";
        public static int Count = 0; // 题目出的数量
        public static int zuode = 0; //做的题目数量
        public static int zhengque = 0;
        public static int lefttime;
        public static int time;
        public static int sum;
        int i =0;
        private void Form1_Load(object sender, EventArgs e)
        {
          
        }
        private void open_Click(object sender, EventArgs e) //打开文件的方法
        {
            OpenFileDialog TxTOpenDialog = new OpenFileDialog();
            TxTOpenDialog.Filter = "RTF文件(*.RTF)|*.RTF";
            if (TxTOpenDialog.ShowDialog() == DialogResult.OK)
            {
                path = TxTOpenDialog.FileName;
                this.richTextBox1.LoadFile(TxTOpenDialog.FileName, RichTextBoxStreamType.RichText);
                save.Enabled = false;
                open.Enabled = false;
                MessageBox.Show("读取成功", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
            }
        }

        private void save_Click(object sender, EventArgs e) //保存文件的方法
        {
            SaveFileDialog TxtSaveDialog = new SaveFileDialog();
            TxtSaveDialog.Filter = "RTF文件(*.RTF)|*.RTF";
            if (File.Exists(path))
            {

                this.richTextBox1.LoadFile(path, RichTextBoxStreamType.RichText);
                MessageBox.Show("保存成功", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
                this.richTextBox1.Clear();
                save.Enabled = false;
            }
            else
            {
                if (TxtSaveDialog.ShowDialog() == DialogResult.OK)
                {

                    this.richTextBox1.SaveFile(TxtSaveDialog.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 richTextBox1_TextChanged(object sender, EventArgs e)
        {
            save.Enabled = true;
            if (this.richTextBox1.Text == "" || this.richTextBox1.Text == null)
            {
                open.Enabled = true;
            }
        }
        private void open2_Click(object sender, EventArgs e) //打开试题的方法
        {
            OpenFileDialog TxTOpenDialog = new OpenFileDialog();
            TxTOpenDialog.Filter = "RTF文件(*.RTF)|*.RTF";
            if (TxTOpenDialog.ShowDialog() == DialogResult.OK)
            {
                path = TxTOpenDialog.FileName;
                this.richTextBox2.LoadFile(TxTOpenDialog.FileName, RichTextBoxStreamType.RichText);
                save.Enabled = false;
                open.Enabled = false;
                MessageBox.Show("打开成功", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
            }
        }

        private void daoru_Click(object sender, EventArgs e) //导入试题的方法
        {
            richTextBox2.Text = richTextBox1.Text;
        }

        private void daan1_Click(object sender, EventArgs e)
        {
            if (daan1.Text == "显示答案")
            {
                daan.PasswordChar = Convert.ToChar(0);
                daan1.Text = "隐藏答案";
            }
            else if (daan1.Text == "隐藏答案")
            {
                daan.PasswordChar = ‘.‘;
                daan1.Text = "显示答案";

            }
        }

        private void kaishi_Click(object sender, EventArgs e)
        {
            string[] ll = new string[100];
            ll = File.ReadAllLines("writer.txt");
            textBox1.Text = ll[0];
            string[] lli = new string[100];
            lli = File.ReadAllLines("writer1.txt");
            textBox2.Text = lli[0];
            string[] llp = new string[100];
            llp = File.ReadAllLines("writer2.txt");
            textBox3.Text = llp[0];
            int minute;
            try
            {
                minute = int.Parse(this.shijian.Text);
            }
            catch (System.Exception ex)
            {
                this.shijian1.Text = "输入错误";
                return;
            }
            lefttime = minute;
            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 (lefttime <= 0)
            {
                timer1.Enabled = false;
                MessageBox.Show("答题时间到！");
                textBox4.Enabled = false;
                Form2 frm2 = new Form2();
                frm2.ShowDialog();
            }
            this.shijian1.Text = "剩余时间" + lefttime.ToString() + "秒";
            lefttime--;  
        }

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

        private void button1_Click(object sender, EventArgs e) //请编辑下道题的事件
        {
            Count++;
            ti.Text = Count.ToString();
            StreamWriter writer = File.AppendText("writer.txt");
            writer.WriteLine(left.Text);
            writer.Close();
            StreamWriter writer1 = File.AppendText("writer1.txt");
            writer1.WriteLine(fuhao.Text);
            writer1.Close();
            StreamWriter writer2 = File.AppendText("writer2.txt");
            writer2.WriteLine(right.Text);
            writer2.Close();
            richTextBox1.Text += left.Text + fuhao.Text + right.Text + label2.Text + "" + "\n";
            left.Clear();
            fuhao.Clear();
            right.Clear();
        }
        private void textBox4_KeyDown(object sender, KeyEventArgs e)
        {
            
            try //异常处理机制，预防数组发生越界
            {
            Environment environment=null;
            double a = Convert.ToDouble(textBox1.Text); //为相关的变量赋值
            double b = Convert.ToDouble(textBox3.Text);
            string m = textBox2.Text;
            int result;
            switch (m)
            {
                case "+":
                    environment = new Environment(new Add()); //策略模式的引用
                    break;
                case "-":
                    environment = new Environment(new Sub());

                    break;
                case "*":
                    environment = new Environment(new Mul());

                    break;
                case "/":
                    environment = new Environment(new Div());

                    break;
                default:
                    break;
            }
            
            if (e.KeyCode == Keys.Enter)
            {
               
                if (int.TryParse(textBox4.Text, out result) == false)
                {
                    MessageBox.Show("请输入数字");
                }
                string answer = environment.Cal(a, b, m).ToString();
                daan.Text += answer + "\r\n";
                if (textBox4.Text == answer.ToString())
                {
                    MessageBox.Show("回答正确");
                    zuode++;
                    zhengque++;   
                }
                else
                {
                    MessageBox.Show("回答错误");
                    zuode++;
                }
                i++;
                textBox4.Clear();
                string[] ll = new string[100];
                ll = File.ReadAllLines("writer.txt");
                textBox1.Text = ll[i];
                string[] lli = new string[100];
                lli = File.ReadAllLines("writer1.txt");
                textBox2.Text = lli[i];
                string[] llp = new string[100];
                llp = File.ReadAllLines("writer2.txt");
                textBox3.Text = llp[i];          
             }  
            }
            catch(Exception ex)
            {
                Form2 frm = new Form2();
                frm.ShowDialog();
            }

        }
        private void button2_Click(object sender, EventArgs e) //清空上次编辑试题的方法
        {
            qita aaa = new qita();
            aaa.qingkong();
        }
        private void button3_Click(object sender, EventArgs e) //退出程序的方法
        {
            Application.Exit();
        }
    }
}