继承

老书上找来的代码

using System;

namespace jicheng
{
    class myApp
    {
        public class A
        {
            public virtual void Fun1(int i)
            {
                Console.WriteLine(i);
            }
            public void Fun2(A a)
            {
                a.Fun1(1);
                Fun1(5);
            }
        }
        public class B : A
        {
            public override void Fun1(int i)
            {
                base.Fun1(i+1);
            }
        }
        public static void Main()
        {
            B b = new B();
            A a = new A();
            a.Fun2(b);
            b.Fun2(a);
        }
    }
}