我是新手，今天碰见了个题，求大神帮忙

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;   // 引用命名空间

namespace ConsoleOne
{
    class Program   
    {
        #region  主函数

        static void Main(string[] args)           
        {
            Animal mammal = new Animal();
            mammal.Name = "犬类";
            mammal.Age = 5;
            Console.WriteLine("{0}的年龄是{1}。", mammal.Name, mammal.Age);
            Dog dog = new Dog();
            dog.Name = "赛虎";
            dog.Age = 3;
            Console.WriteLine("{0}......{1}的年龄是{2}。",dog.Hello(), dog.Name, dog.Age);
            Console.ReadKey();
        }
        #endregion

        #region  Animal类
        class Animal
            {
                private string name;
                private int age;
                private bool sexual;

                public string Name
                {
                    set
                    {
                        this.name = value; // value代表用户赋值过来的值
                    }
                    get
                    {
                        return this.name;
                    }
                }

                public int Age
                {
                    set
                    {
                        this.age = value;

                    }
                    get
                    {
                        return this.age;
                    }
                }

                public void Eating()
                {
                    Console.WriteLine("Having a meal.");
                }
            };
        #endregion

        #region  Dog类 从Animal类继承
        class Dog: Animal
        {
            public string Hello()
            {
                return("Wang! Wang! Wang!");
            }
        };
        #endregion
    }
}