简单工厂模式——学习《大话设计模式》

最近一段时间在学习《大话设计模式》，我觉得这本真的很不错，以下是我学习第一章 简单工厂模式后整理的代码，请大家多指导，小弟刚出炉。

//运算类
public class Operation
{
    private double _numberA=0;
    private double _numberB=0;
    
    public double NumberA
    {
        set
        {
            _numberA=value;
        }
        get
        {
            return _numberA;
        }
    }
    public double NumberB
    {
        set
        {
            _numberB=value;
        }
        get
        {
            return _numberB;
        }
    }
    public virtual double GetResult()
    {
        double result=0;
        return result;
    }
}
//加法运算子类
public class OperationAdd:Operation
{
    public override double GetResult()
    {
        double result=0;
        result=NumberA+NumberB;
        return result;
    }
}
//减法运算子类
public class OperationSub:Opertion
{
    public override double GetResult()
    {
        double result=0;
        result=NumberA-NumberB;
        return result;
    }
}
//乘法运算子类
public class OperationMul:Operation
{
    public override double GetResult()
    {
        double result=0;
        result=NuberA*NumberB;
        return result;
    }
}

//除法运算子类
public class OperationDiv:Operation
{
    public override double GetResult()
    {
        double result=0;
        if(NumberB==0)
            throw new Exception("除数不能为零");
        result=NumberA/NumberB;
        return result;
    }
    
}
//简单工厂类
public class OperationFactory
{
    public static Operation createOperate(string operate)
    {
        
        Operration oper=null;
        swith(operate)
        {
            case "+":
                oper=new OperationAdd();
            break;
            case "-":
                oper=new OperationSub();
            break;
            case "*":
                oper=new OperationMul();
            break;
            case "/":
                oper=new OperationDiv();
            break;
        }
        return oper;
           
    }
   

}
//客户端调用代码
public class Client
{
    public static void Main(string[] args)
    {
        Operation oper;
        oper=OperationFactory.createOperate("+");
        oper.NumberA=1;
        oper.NumberB=2;
        double result=oper.GetResult();
        
    }
}