大话设计模式：简单工厂模式(C#版)

opertation.cs

public class Operation
{
    private double _numberA = 0;
    private double _numberB = 0;
    
    public double NumberA
    {
        get { return _numberA; }
        set { _numberA = value; }
    }
    public double NumberB
    {
        get { return _numberB; }
        set { _numberB = value; }
    }
    public virtual double GetResult()
    {
        double result = 0;
        return result;
    }
}

class OperationAdd : Operation
{
    public override double GetResult()
    {
        double result = 0;
        result = NumberA + NumberB;
        return result;
    }
}

class OperationSub : Operation
{
    public override double GetResult()
    {
        double result = 0;
        result = NumberA - NumberB;
        return result;
    }
}

class OperationMul : Operation
{
    public override double GetResult()
    {
        double result = 0;
        result = NumberA * NumberB;
        return result;
    }
}

class OperationDiv : Operation
{
    public override double GetResult()
    {
        double result = 0;
        if (NumberB ==0):
            throw new Exception("除数不能为0。");
        result = NumberA / NumberB;
        return result;
    }
}

public class OperationFactory
{
    public static Operation createOperate(string operate)
    {
      Operation oper = null;
      switch (operate)
      {
          case "+":
              oper = new OperationAdd();
              break;
          case "-":
              oper = new operationSub();
              break;
          case "*":
              oper = new OperationMul();
              break;
          case "/":
              oper = new operationDiv();
              break;
      }
      return oper;
    }
}

/// 客户端代码
Operation oper;
oper = OperationFactory.createOperate("+");
oper.NumberA = 1;
oper.NumberB = 2;
double result = oper.GetResult();
Opera