c#之重写

 class Program
    {
        static void Main(string[] args)
        {
            person re = new Human();//声明父类实例化子类
            Human hu = new Human();
            re.SayHello();
            hu.SayHello();
            Console.ReadKey();
        }
    }

class person
    { 
        
        /// <summary>
        /// 姓名
        /// </summary>
        private string name;

        public string Name
        {
            get { return name; }
            set { name = value; }
        } 
        #endregion

        #region 年纪
        /// <summary>
        /// 年纪
        /// </summary>
        private int age;

        public int Age
        {
            get { return age; }
            set { age = value; }
        }
        #endregion

        #region 性别
        /// <summary>
        ///性别
        /// </summary>

        private bool sex;

        public bool Sex
        {
            get { return sex; }
            set { sex = value; }
        } 
        #endregion
        public virtual void SayHello() {}
        public person()
        {

        }
    }

 class Human : person
    {
        public override void SayHello()
        {
            Console.WriteLine("nii");
        } 
        public Human()  
        {

        }
    }