简单工厂模式

class Operation
{
public double NumberA { get; set; }
public double NumberB { get; set; }
public virtual double getResult()
{
return 0.0;
}
}

class OperationAdd : Operation
{
public override double getResult()
{
return NumberA + NumberB;
}
}

class OperationSub : Operation
{
public override double getResult()
{
return NumberA - NumberB;
}
}

class OperationFactory
{
public static Operation createOperate(string operate)
{
Operation o = null;
switch (operate)
{
case "+":
o = new OperationAdd();
break;
case "-:":
o = new OperationSub();
break;
}
return o;
}
}

static void Main(string[] args)
{
Operation oper = OperationFactory.createOperate("+");
oper.NumberA = 3;
oper.NumberB = 5;
Console.WriteLine(oper.getResult());

}