new关键字对类成员的阻断

 

昨天终于对new关键字对类成员的阻断作用有了比较清晰的认识，“对类成员的阻断”是王涛大哥在其作品《你必须知道的.NET》的说法，昨天在园里看到一位前辈戏称之为“封印咒术”，我感觉这个说法很贴切。比如Sons类继承自Fathers类，在Sons中对Fathers的虚方法DoVirtualWork()实现了封印，则以后继承自Sons的类就无法继承Fathers的DoVirtualWork()方法。代码如下：

    public class Fathers
    {
        public void DoWork()
        {
            Console.WriteLine("Father.DoWork()");
        }

        public virtual void DoVirtualWork()
        {
            Console.WriteLine("Father.DoVirtualWork()");
        }
    }

    public class Sons : Fathers
    {
       public new void DoVirtualWork()
        {
            //base.DoVirtualWork();
            Console.WriteLine("Son.DoVirtualWork()");
        }

      }

    public class Grandsons : Sons
    {
        
     }

    public class Sonson : Sons
    {
        
    }
    class Program
    {
        static void Main(string[] args)
        {
            //调用Sons.DoVirtualWork()         
            Sons person1 = new Grandsons();
            person1.DoVirtualWork();
            //调用Sons.DoVirtualWork()
            Sons person2 = new Sons();
            person2.DoVirtualWork();
            //调用Fathers.DoVirtualWork()
            Fathers person = new Grandsons();
            person.DoVirtualWork();
            //调用Fathers.DoVirtualWork()
            Fathers person3 = new Sonson();
            person3.DoVirtualWork();
            //调用Sons.DoVirtualWork()
            Sonson person4 = new Sonson();
            person4.DoVirtualWork();
            Console.Read();
        }
    }

 

运行结果：

Son.DoVirtualWork()
Son.DoVirtualWork()
Father.DoVirtualWork()
Father.DoVirtualWork()
Son.DoVirtualWork()

所以，在类的设计中尽可能不用new阻断类成员。