求高手指点 一个简单的打分系统

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;namespace StudentScore
{
    public class Student
    {
        string name;
        int score;        public int GiveScore(int amount)
        {
            if (amount > 0)
            {
                score += amount;
                return amount;
            }
            else
            {
                MessageBox.show("加分" + amount + "不是一个合理的值");
                return 0;
            }
        }        public int TakeOffScore(int amount)
        {
            if (Score >= amount && amount > 0)
            {
                Score -= amount;
                return amount;            }
            else
            {
                MessageBox.Show("减分" + amount + "不是一个合理的值");
                return 0;
            }        }
    }}
namespace WindowsForms1
{
  
    public partial class Form1 : Form
    {
        Student zhangfei, liubei;
        public void UpdateForm()
        {
            label3.Text = zhangfei.Name + "have" + zhangfei.Score + "分";
            label4.Text = liubei.Name + "have" + liubei.Score + "分";
        
        }
      
        public Form1()
        {
            InitializeComponent();            zhangfei=new Student();
            liubei=new Student();
            zhangfei.Name="zhangfei";
            zhangfei.Score = 100;
            liubei.Name = "liubei";
            liubei.Score = 100;
            UpdateForm;
        }        private void Form1_Load(object sender, EventArgs e)
        {        }        private void button1_Click(object sender, EventArgs e)
        {
            zhangfei.GiveScore(5);
            UpdateForm;
        }        private void button2_Click(object sender, EventArgs e)
        {
            liubei.TakeOffScore(3);
            UpdateForm;
        }
    }
}《提示没有student这个空间，我是新手，看了下我的studnet写的是public啊》