封装，多态和继承的例子

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

namespace jichengchonggou
{
    public class Animal
    {
        //获得声音的方法
        public virtual string GetShoutSound()
        {
            return "";
        }
    }
}

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

namespace jichengchonggou
{
    public class Dog : Animal
    {
        public override string GetShoutSound()
        {
            return "旺旺旺旺!!!!!";
        }
    }
}

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

namespace jichengchonggou
{
    public class Cat : Animal
    {
        public override string GetShoutSound()
        {
            return "喵喵喵喵!!!!!";
        }
    }

}

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

namespace jichengchonggou
{
    internal class Program
    {
        private static void Main(string[] args) //主函数 
        {
            Animal animal1 = new Dog();
            Animal animal2 = new Cat();
            string a1 = animal1.GetShoutSound();
            string a2 = animal2.GetShoutSound();
            Console.WriteLine(a1 + a2);
        }
    }
}