设计模式-3-工厂方法

 public abstract class AbsProduct
    {
        public abstract void Exc();
    }
  class ProductA1 : AbsProduct
    {
        public override void Exc()
        {
            Console.WriteLine("A1");
        }
    }
   class ProductB1 : AbsProduct
    {
        public override void Exc()
        {
            Console.WriteLine("B1");

        }
    }
   public abstract class AbsCreator
    {
        public abstract AbsProduct GetProduct(string str);
    }
  public class CreatorA : AbsCreator
    {
        public override AbsProduct GetProduct(string str)
        {
            if(str=="a")
            {
                return new ProductA1();
            }
            return null;
        }
    }
 public class CreatorB : AbsCreator
    {
        public override AbsProduct GetProduct(string str)
        {
            if(str=="b")
            {
                return new ProductB1();
            }
            return null;
        }
    }
            AbsCreator c1 = new CreatorA();
            AbsCreator c2 = new CreatorB();
            c1.GetProduct("a").Exc();
            c2.GetProduct("b").Exc();