自己动手写计算器v1.0

       今天突发奇想，想着看了还几个设计模式了，倒不如写点东西来实践它们。发现计算器这种就比较合适，打算随着设计模式的学习，会对计算器不断的做改进。

包括功能的增加和算法的改进。初学者难免犯错，希望大家不吝指教。

　　　　计算器V1.0：主要实现了计算器最常见的加减乘除功能，同时还有一个特殊功能，例如：我们执行完1+2后，如果点击等号，会执行加法运算输出结果。但我们如果点击的是运算符（如-），那么不仅会执行加法运算，还会将-号放置到执行结果后，表示这次执行的将会是减法运算。

　　　　代码:Operator类负责使用简单工厂模式来生成加减乘除运算。

Form窗体后台代码：

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

namespace 计算器
{
    public partial class Form1 : Form
    {
        //简述：变量集中声明处
        StringBuilder num1 = new StringBuilder();
        StringBuilder num2 = new StringBuilder();
        public void CheckTextbox(string num)
        {
            StringBuilder str = new StringBuilder();
            if (this.textBox1.Text != "")
            {
                str.Append(this.textBox1.Text);
                str.Append(num);
                this.textBox1.Text = str.ToString();
            }
            else
            {
                this.textBox1.Text = num;
            }
        }
        //简述：输入运算符。 2016-5-13 张杨
        public void CheckYunSuan(string myOperator)
        {
            StringBuilder str = new StringBuilder();
            if (this.textBox1.Text != "")
            {
                if (textBox1.Text.Contains("+") || textBox1.Text.Contains("-") || textBox1.Text.Contains("*") || textBox1.Text.Contains("/"))
                {
                    ShowResult();
                }
                str.Append(this.textBox1.Text);
                str.Append(myOperator);
                this.textBox1.Text = str.ToString();
            }
            else
            {
                this.textBox1.Text = myOperator;
            }
        }

        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            CheckTextbox("1");
        }

        private void button2_Click(object sender, EventArgs e)
        {
            CheckTextbox("2");
        }

        private void button3_Click(object sender, EventArgs e)
        {
            CheckTextbox("3");
        }

        private void button4_Click(object sender, EventArgs e)
        {
            CheckTextbox("4");
        }

        private void button5_Click(object sender, EventArgs e)
        {
            CheckTextbox("5");
        }

        private void button6_Click(object sender, EventArgs e)
        {
            CheckTextbox("6");
        }

        private void button7_Click(object sender, EventArgs e)
        {
            CheckTextbox("7");
        }

        private void button8_Click(object sender, EventArgs e)
        {
            CheckTextbox("8");
        }

        private void button9_Click(object sender, EventArgs e)
        {
            CheckTextbox("9");
        }
        //简述：下面的为加减乘除功能。
        //2016-5-13 张杨

        private void button10_Click(object sender, EventArgs e)
        {
            CheckYunSuan("+");
        }

        private void button11_Click(object sender, EventArgs e)
        {
            CheckYunSuan("-");
        }

        private void button12_Click(object sender, EventArgs e)
        {
            CheckYunSuan("*");
        }

        private void button13_Click(object sender, EventArgs e)
        {
            CheckYunSuan("/");
        }

        private void button14_Click(object sender, EventArgs e)
        {
            this.textBox1.Text = String.Empty;
        }
        //简述：判断字符是否为运算符。 2016-5-13  张杨
        public bool isOperator(char key)
        {
            if (key == '+' || key == '-' || key == '*' || key == '/')
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        //简述：计算结果。  2016-5-13    张杨
        private void ShowResult()
        {
            string strText = this.textBox1.Text;
            char myOperator = 'A';
            int flag = 0;
            string result = "";
            foreach (char key in strText)
            {


                if (isOperator(key))
                {
                    flag = 1;
                    myOperator = key;
                    continue;
                }
                else
                {
                    switch (flag)
                    {
                        case 0: num1.Append(key); break;
                        case 1: num2.Append(key); break;
                    }
                }
            }

            result = OperatorFactory.GetResult(myOperator, double.Parse(num1.ToString()), double.Parse(num2.ToString()));
            num1 = num1.Remove(0, num1.Length);
            num2 = num2.Remove(0, num2.Length);
            this.textBox1.Text = result;
        }
        private void button15_Click(object sender, EventArgs e)
        {
            ShowResult();
        }
    }
}

重点来了，Operator类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 计算器
{
    //简述：加减乘除处理类，采用了简单工厂模式。 2016-5-13 张杨
    class Operator
    {
        public virtual string GetResult(double num1, double num2)
        {
            return "error";
        }
    }
    public class OperatorFactory
    {
       static Operator myOperator=new Operator();
        public static string GetResult(char key,double num1,double num2)
        {
            switch (key)
            {
                case '+': myOperator = new plusOperator(); break;
                case '-': myOperator = new jianOperator(); break;
                case '*': myOperator = new chenOperator(); break;
                case '/': myOperator = new chuOperator(); break;
            }
            return myOperator.GetResult(num1,num2);
        }
    }
    class plusOperator : Operator
    {
        public  override string GetResult(double num1, double num2)
        {
            return (num1 + num2).ToString();
        }
    }
    class jianOperator : Operator
    {
        public override string GetResult(double num1, double num2)
        {
            return (num1 - num2).ToString();
        }
    }
    class chenOperator : Operator
    {
        public override string GetResult(double num1, double num2)
        {
            return (num1 * num2).ToString();
        }
    }
    class chuOperator : Operator
    {
        public override string GetResult(double num1, double num2)
        {
            if (num2 == 0)
            {
                return "除数不能为0";
            }
            else
            {
                return (num1 / num2).ToString();
            }
        }
    }
}

运行结果：