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 = ;
             result = x + y;
             return result;
         }
     }
     public class Sub : Calculator
     {
         public override double Cal(double x, double y)
         {
             double result = ;
             result = x - y;
             return result;
         }
     }
     public class Mul : Calculator
     {
         public override double Cal(double x, double y)
         {
             double result = ;
             result = x * y;
             return result;
         }
     }
     public class Div : Calculator
     {
         public override double Cal(double x, double y)
         {
             double result = ;
             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 == )
          {
              opear = new Opear(new Add());
          }
          else if (DropDownList1.SelectedIndex == )
          {
            opear  = new Opear(new Sub());
          }
          else if (DropDownList1.SelectedIndex == )
          {
              opear = new Opear(new Mul());
          }
          else if (DropDownList1.SelectedIndex == )
          {
              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：