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

namespace ConsoleApp1 
{
    /// <summary>
    /// 胡萝卜类
    /// </summary>
    class Carrot : Vegetables
    {
        public static void Main(string[] args) {
            Vegetables c = new Carrot();
            if (c is Carrot) {//is关键字：如果转成功则返回true,否则返回false
                Console.WriteLine("is---->蔬菜类型胡萝卜对象转胡萝卜成功");
            } 
            Eggplant e = c as Eggplant;//as关键字：如果转成功返回需要转换的类型，如果失败返回null
            if (e == null) {
                Console.WriteLine("as---->胡萝卜转茄子失败");
            }
            Eggplant ee = new Eggplant();
            Vegetables vv = ee as Vegetables;
            if (vv != null) {
                Console.WriteLine("as--->胡萝卜转蔬菜类成功");
            }
            Eggplant cc = c as Eggplant;
            if (cc == null) {
                Console.WriteLine("as--->胡萝卜转茄子类失败");
            }
            if (!(c is Eggplant)) {
                Console.WriteLine("is--->胡萝卜转茄子类失败");
            }

        }
    }
}

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

namespace ConsoleApp1
{
    /// <summary>
    /// 茄子类
    /// </summary>
    class Eggplant : Vegetables
    {
    }
}

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

namespace ConsoleApp1
{
    /// <summary>
    /// 蔬菜类
    /// </summary>
    class Vegetables
    {
    }
}