DataGridView和ListT绑定不显示问题

在学习DataGridView 和List<T>绑定时发现DataGridView不会显示数据。后来发现要用类的属性才能正常显示，如果直接用类的字段等来显示，则无法显示数据。

代码如下：

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 WindowsFormsApplication20
{public partial class Form1 : Form{public Form1(){InitializeComponent();}private void Form1_Load(object sender, EventArgs e){dgv_message.GridColor = Color.Blue;           dgv_message.DataSource = new List<student>(){new student(){sName="小李",Age=20},new student(){sName="小张",Age=40},new student(){sName="小王",Age=60},new student(){sName="小黄",Age=22}};dgv_message.Columns[0].HeaderText = "姓名";dgv_message.Columns[1].HeaderText = "年龄";}}public class student{private string name;private  int age;public string sName{get { return name; }set { name = value; }}public int Age{get { return age; }set { age =value ; }}}
}

如果把student中类变成以下代码，则无法显示：

    public class student{public string sName;public int Age;      }