今天发现C#虚函数简直妙不可言....

 

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            //A a = new A();
            //B b = new B();
            C c = new C();
            //b.GetYear();
        }
    }

    public class A
    {
        public A()
        {
            Console.WriteLine("DEBUG: A constructing");
           
            this.GetYear();
        }

        public virtual void GetYear()
        {
            Console.WriteLine("A");
        }
    }

    public class B:A
    {
        public B():base()
        {
            Console.WriteLine("DEBUG: B constructing");
            this.GetYear();
        }

        public override void GetYear()
        {
            //base.GetYear();
            Console.WriteLine("B");
        }
    }

    public class C : B
    {
        public C()
        {
            Console.WriteLine("DEBUG : C constructing");
            this.GetYear();
        }

        public override void GetYear()
        {
            //base.GetYear();
            Console.WriteLine("C");
        }

    }
   

}

 

运行结果:一定大出你的意料吧!

 

 如果把代码改一下:

 

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication2
...{
    class Program
    ...{
        static void Main(string[] args)
        ...{
            //A a = new A();
            C c = new C();

            // c.GetYear();
            //b.GetYear();
        }
    }

    public class A
    ...{
        public A()
        ...{
            Console.WriteLine("DEBUG: A constructing");
            this.GetYear();
        }

        protected  void GetYear()
        ...{
            Console.WriteLine("A");
        }
    }

    public class B:A
    ...{
        public B():base()
        ...{
            Console.WriteLine("DEBUG: B constructing");
            this.GetYear();
        }

        protected void GetYear()
        ...{
            //base.GetYear();
            Console.WriteLine("B");
        }
    }

    public class C : B
    ...{
        public C():base()
        ...{
            Console.WriteLine("DEBUG: C constructing");
            //base.GetYear();
            this.GetYear();
        }

        protected void  GetYear()
        ...{
            //base.GetYear();
            Console.WriteLine("C");
        }
    }

}

通过这两个例子,终于好像彻底明白了虚函数和new(子类屏蔽父类的方法的关键字).

不过还有更cool点儿的.....请看下面的例子,仔细看小心头晕哦,哈:)

 

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication2
...{
    class Program
    ...{
        static void Main(string[] args)
        ...{
            //A a = new A();
            //C c = new C();
            D d = new D();

            // c.GetYear();
            //b.GetYear();
        }
    }

    public class A
    ...{
        public A()
        ...{
            Console.WriteLine("DEBUG: A constructing");
            this.GetYear();
        }

        protected virtual void GetYear()
        ...{
            Console.WriteLine("A");
        }
    }

    public class B:A
    ...{
        public B():base()
        ...{
            Console.WriteLine("DEBUG: B constructing");
            this.GetYear();
        }

        //protected override void GetYear()
        //{
        //    //base.GetYear();
        //    Console.WriteLine("B");
        //}
    }

    public class C : B
    ...{
        public C():base()
        ...{
            Console.WriteLine("DEBUG: C constructing");
            //base.GetYear();
            this.GetYear();
        }

        protected override void  GetYear()
        ...{
            //base.GetYear();
            Console.WriteLine("C");
        }
        
        //protected new  void GetYear()
        //{
        //    //base.GetYear();
        //    Console.WriteLine("C");
        //}

    }

    public class D : C
    ...{
        public D()
        ...{
            Console.WriteLine("DEBUG: D contructing");
            this.GetYear();
        }

    }

}

怎么样,发现了吧.虚函数和new的确有很多相似的地方,甚至如果仅以实现程序为目的的话,应该可以互换的,不是吗?

听起来怎么有点玄啊!没错,肯定不是的.是很相似,不过肯定有不一样的地方.可在哪里呢?