c#设计模式之简单工厂

1.面向对象的3大属性，封装、继承、多态，以一个加单的计算机为例：

创建一个父类Operation 有两个属性和一个计算方法（虚方法），便于子类重写：

  1  public class Operation
  2     {
  3         private double _numberA = 0;
  4         private double _numberB = 0;
  5 
  6         public double NumberA
  7         {
  8             get { return _numberA; }
  9             set { _numberA = value; }
 10         }
 11 
 12         public double NumberB
 13         {
 14             get { return _numberB; }
 15             set { _numberB = value; }
 16         }
 17 
 18         /// <summary>虚方法
 19         /// 
 20         /// </summary>
 21         /// <returns></returns>
 22         public virtual double GetResult()
 23         {
 24             double result = 0;
 25             return result;
 26         }
 27     }

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接下来创建计算类，加减乘除类来集成操作类

加类

  1  public 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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减类

  1  public 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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乘类

  1  public 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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除类

  1  public class OperationDiv:Operation
  2     {
  3         public override double GetResult()
  4         {
  5             double result = 0;
  6             if (NumberB == 0)
  7                 throw new Exception("除数不能为0");
  8             result = NumberA / NumberB;
  9             return result;
 10         }
 11     }

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然后通过简单工厂类来创建计算的实例

  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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最后通过界面去调用：

  1  static void Main(string[] args)
  2         {
  3             Operation oper;
  4             oper = OperationFactory.createOperate("+");
  5             oper.NumberA = 1;
  6             oper.NumberB = 2;
  7             double result = oper.GetResult();
  8             Console.WriteLine(result);
  9             Console.ReadKey();
 10         }

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这里把计算过程都封装成一个方法，每个计算类又集成了操作类，这样由于每个方法都重写了计算方法，这里表现出一个方法的不同表现形态，如果以后要增加其他的方法，只需要继承操作类重写计算方法即可，这样也不会对原有的程序进行修改，实现了解耦，面向对象语言的优点在于可维护性，可复用，可扩展、灵活性。

以上为自学的一点总结，希望有不对的地方，请大家指点，谢谢