c#中Hashtable方法返回值的探索

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

namespace ConApp
{
    class Student
    {
        string name;

        public string Name
        {
            get { return name; }
            set { name = value; }
        }
        ulong stuID;

        public ulong StuID
        {
            get { return stuID; }
            set { stuID = value; }
        }


        double chinese;

        public double Chinese
        {
            get { return chinese; }
            set { chinese = value; }
        }
        double math;

        public double Math
        {
            get { return math; }
            set { math = value; }
        }
        double english;

        public double English
        {
            get { return english; }
            set { english = value; }
        }

        public double ComputeAvg()
        {
            return (english + math + chinese) / 3;
        }


    }

    class Program
    {
        static void Main(string[] args)
        {
            Student stu = new Student();
            stu.Name = "wang";
            stu.StuID = 123;

            Hashtable ht = new Hashtable();
            ht.Add(stu.StuID,stu);
            Student stutemp;
            foreach (DictionaryEntry de in ht)
            {
                stutemp = (Student)ht[de.Key];
                Console.WriteLine("学生姓名:{0}\n学生学号:{1}\n", stutemp.Name, stutemp.StuID);
            }
            stu.Name = "张";
            stu.StuID = 456;
            Student temp;
            foreach (DictionaryEntry de in ht)
            {
                temp = (Student)ht[de.Key];
                Console.WriteLine("学生姓名:{0}\n学生学号:{1}\n", temp.Name, temp.StuID);
            }
            ulong id = 123;
            temp = (Student)ht[id];
            temp.Name = "song";
            temp.StuID = 999;
            foreach (DictionaryEntry de in ht)
            {
                stutemp = (Student)ht[de.Key];
                Console.WriteLine("学生姓名:{0}\n学生学号:{1}\n", stutemp.Name, stutemp.StuID);
            }
            Student newStu = new Student();
            newStu = (Student)ht[id];
            newStu.Name = "uuuu";
            newStu.StuID = 1000;
            foreach (DictionaryEntry de in ht)
            {
                stutemp = (Student)ht[de.Key];
                Console.WriteLine("学生姓名:{0}\n学生学号:{1}\n", stutemp.Name, stutemp.StuID);
            }
        }
    }
}