/// <summary>
  /// 抽象工厂，声明了一个创建Product的方法
  /// </summary>
  public abstract class Creator
  {
    /// <summary>
    /// 该方法用来返回Product产品
    /// </summary>
    /// <returns></returns>
    public abstract Product CreateProduct();
  }

  /// <summary>
  /// 具体产工厂，产品类 A 的创建者，继承自抽象工厂Creator
  /// </summary>
  public class ProductACreator : Creator
  {
    public override Product CreateProduct()
    {
      return new ConcreteProductA();
    }
  }

  /// <summary>
  /// 具体产工厂，产品类 B 的创建者，继承自抽象工厂Creator
  /// </summary>
  public class ProductBCreator : Creator
  {
    public ProductBCreator() { }

    public override Product CreateProduct()
    {
      return new ConcreteProductB();
    }
  }

  /// <summary>
  /// 抽象产品，定义工厂方法中所创建的对象
  /// </summary>
  public abstract class Product
  {
    public Product()
    { }

    public abstract void Opration();
  }

  /// <summary>
  /// 具体产品A，继承自Product
  /// </summary>
  public class ConcreteProductA : Product
  {
    public ConcreteProductA() { }

    public override void Opration()
    {
      // This is product A
    }
  }

  /// <summary>
  /// 具体产品B，继承自Product
  /// </summary>
  public class ConcreteProductB : Product
  {
    public ConcreteProductB() { }

    public override void Opration()
    {
      // This is product B
    }
  }