疑惑的virtual method

 

 class A
    {

public virtual void fun(int i)
        {
            Console.WriteLine(i);
        }
public void fun2(A a)
        {
            a.fun(1);
            fun(5);
        }
    }
class B:A
    {

public override void fun(int i)
        {
base.fun(i+1);
        }
    }
class Program
    {
static void Main(string[] args)
        {
            A a = new A();
            B b = new B();
            a.fun2(b);
            b.fun2(a);

        }
    }