void Main(){    Factory.ChooseFactory("A").GetProduct().Dump();    Factory.ChooseFactory("B").GetProduct().Dump();}class Product{}class ProductA:Product{}class ProductB:Product{}abstract class Factory{    public static Factory ChooseFactory(string name){        switch (name)        {            case "A":return new FactoryA();            case "B":return new FactoryB();            default:return null;        }    }    public abstract Product GetProduct();}class FactoryA:Factory{    public override Product GetProduct(){return new ProductA();}}class FactoryB:Factory{    public override Product GetProduct(){return new ProductB();}}