Design Patterns 01 - 简单工厂模式

public class Operation {
    public static double GetResult(double, double, string) {
        //todo
    }
}
public static void Main(string[] args) {
    Console.Write(GetResult(a, b, op));
}

public class Operation {
    private double _numberA;
    private double _numberB;
    public double NumberA {
        get {
            return _numberA;
        };
        set {
            _numberA = value;
        };
    }
    public double NumberB {
        get {
            return _numberB;
        };
        set {
            _numberB = value;
        };
    }

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

public class OperationFactory {
    public static Operation CreateOperation(string operator) {
        Operation operation = null;
        switch(operator) {
            case "+" :
                operation = new OperationAdd();
                break;
            default:
                break;
        }
        return operation;
    }
}

public static void Main(string[] args) {
    Operation operation = OperationFactory.CreateOperation("+");
}