c# 多态 虚方法

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

namespace 飞行棋
{
     public class A
     {
         public virtual void Fun1(int i)
         {
             Console.WriteLine(i);
         }
         public void Fun2(A a)
         {
             a.Fun1(1);
             Fun1(5);
         }
     }
     class Program:A
     {
         public override void Fun1(int i)
         {
             base.Fun1(i+1);
         }
         static void Main(string[] args)
         {
             Program b = new Program();
             A a = new A();
             a.Fun2(b);          //2   5
             b.Fun2(a);          //1   6
             Console.ReadLine();
         }
     }
      
    
      public abstract class A
     {
         public A()
         {
             Console.WriteLine(‘A‘);
         }
         public virtual void Fun()
         {
             Console.WriteLine("A.Fun()");
         }
     }
 
     class Program :A
     {
         public Program()
         {
             Console.WriteLine(‘B‘);
         }
         public new void Fun()
         {
             Console.WriteLine("B.Fun()");
         }
         static void Main(string[] args)
         {
             A a = new Program();
             a.Fun();        // A  B  A.Fun()
             Console.ReadLine();
         }
     }
  
 
     class BaseClass
     {
         public virtual int Add(int x,int y)
         {
             return x+y;
         }
     }
     class Program:BaseClass
     {
         static int z = 100;
         public override int Add(int x, int y)
         {
             return base.Add(x,y)+z; //300
             // return x * y; 50
         }
          static void Main(string[] args)
         {
             BaseClass baseclass = new Program();
             Console.WriteLine(baseclass.Add(10,5));
             Console.ReadLine();
         }      
     }
}