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

namespace _0080703_6
{
    class Program
    {
        class A
        {
            public virtual void F1(int i)
            {
                Console.WriteLine(i);
            }
            public void F2(A a)
            {
                a.F1(1);
                F1(5);
            }
            public class B : A
            {
                public override void F1(int i)
                {
                    base.F1(i + 1);
                }
            }
            static void Main(string[] args)
            {
                B b = new B();
                A a = new A();
                a.F2(b);
                b.F2(a);
                Console.ReadLine();
            }
        }
    }
}
  有哪个高手指点一下   这好像是类的继承

能不能详细点 说些继承的要点吧