设计模式之☞简单工厂模式

通过多态制作一个简单的计算器

operation类：

 1    public class operation
 2     {
 3         private double _numbera = 0;
 4         private double _numberb = 0;
 5         public double numbera
 6         {
 7             get
 8             {
 9                 return _numbera;
10             }
11 
12             set
13             {
14                 _numbera = value;
15             }
16         }
17         public double numberb
18         {
19             get
20             {
21                 return _numberb;
22             }
23 
24             set
25             {
26                 _numberb = value;
27             }
28         }
29         public virtual double getresult()
30         {
31             double result = 0;
32             return result;
33         }
34     }

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简单工厂类：

 1 public class operationfactory
 2     {
 3         public static operation createoperate(string operate)
 4         {
 5             operation oper = null;
 6             switch (operate)
 7             {
 8                 case "+":
 9                     oper = new operationadd();
10                     break;
11                 case "-":
12                     oper = new operationsub();
13                     break;
14                 case "*":
15                     oper = new operationmul();
16                     break;
17                 case "/":
18                     oper = new operationdiv();
19                     break;
20             }
21             return oper;
22         }
23     }

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加法类，继承operation：

1 class operationadd:operation
2     {
3         public override double getresult()
4         {
5             double result = 0;
6             result = numbera + numberb;
7             return result;
8         }
9     }

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减法类，继承operation：

1     class operationsub:operation
2     {
3         public override double getresult()
4         {
5             double result = 0;
6             result = numbera - numberb;
7             return result;
8         }
9     }

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乘法类，继承operation：

1     class operationmul : operation
2     {
3         public override double getresult()
4         {
5             double result = 0;
6             result = numbera * numberb;
7             return result;
8         }
9     }

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除法类，继承operation：

 1     class operationdiv : operation
 2     {
 3         public override double getresult()
 4         {
 5             double result = 0;
 6             if (numberb==0)
 7             {
 8                 throw new exception("除数不能为0。");
 9             }
10             result = numbera / numberb;
11             return result;
12         }
13     }

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调用：

1         private void button1_click(object sender, eventargs e)
2         {
3             operation oper = operationfactory.createoperate(textbox4.text);
4             oper.numbera =convert.todouble(textbox1.text);
5             oper.numberb = convert.todouble(textbox2.text);
6             textbox3.text = oper.getresult().tostring();
7         }

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