ASP.net四则运算《《《策略模式

Calculator.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
  /// <summary>
  ///Calculator 的摘要说明
  /// </summary>
public abstract class Calculator
{
    public abstract double Cal(double x, double y);
}

    public class Add : Calculator                //接口法运算
    {
        public override double Cal(double x, double y)     //重写
        {
            double result = 0;
            result = x + y;
            return result;
        }
    }
    public class Sub : Calculator
    {
        public override double Cal(double x, double y)
        {
            double result = 0;
            result = x - y;
            return result;
        }
    }
    public class Mul : Calculator
    {
        public override double Cal(double x, double y)
        {
            double result = 0;
            result = x * y;
            return result;
        }
    }
    public class Div : Calculator
    {
        public override double Cal(double x, double y)
        {
            double result = 0;
            result = x / y;
            return result;
        }
    }
    public class Opear           //定义运算符
    {
        private Calculator calculate = null;          //实例化一个基类的引用对象
        public Opear(Calculator calculator)         //calculator为派生类的一个对象
        {
            this.calculate = calculator;                  //把派生类的对象赋给基类的引用对象
        }
        public double Cal(double x, double y, String op)
        {
            return this.calculate.Cal(x, y);         //返回计算结果
        }
    }

ASP.net后台代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    { 
         string op = DropDownList1.SelectedItem.ToString();
         double x = Convert.ToDouble(TextBox1.Text); 
         double y = Convert.ToDouble(TextBox2.Text);
        
         Opear opear =null;
         if (DropDownList1.SelectedIndex == 0)
         {
             opear = new Opear(new Add());    
         }
         else if (DropDownList1.SelectedIndex == 1)
         {
           opear  = new Opear(new Sub());    
         }
         else if (DropDownList1.SelectedIndex == 2)
         {
             opear = new Opear(new Mul());
         }
         else if (DropDownList1.SelectedIndex == 3)
         {
             opear = new Opear(new Div());
         }
         string answer = opear.Cal(x, y, op).ToString(); 
         string result = TextBox1.Text + DropDownList1.SelectedItem.ToString() + TextBox2.Text;
         if (TextBox4.Text == answer)                                 
         {
             Response.Write("<script>alert('回答正确!')</script>");          
             ListBox1.Items.Add(result + "=" + TextBox4.Text.Trim());
         }
 
         else                                                       
         {
             Response.Write("<script>alert('答题错误!')</script>");          
             ListBox1.Items.Add(result + "=" + TextBox4.Text.Trim());  
         }
         TextBox1.Text = "";             
         TextBox2.Text = "";
         TextBox4.Text = "";  
     }
    }

运行结果：

运行界面：