WinForm DataGridView 绑定泛型List(List<T>)/ArrayList不显示的原因和解决

一、问题

WinForm DataGridView 绑定泛型List (List<T>)/ArrayList不显示，UI

代码如下：

using System;using System.Collections.Generic;using System.Data;using System.Data.OleDb;using System.IO;using System.Windows.Forms;namespace WindowsFormsApplication1{    public delegate T BorrowReader<out T>(IDataReader reader);    public partial class FormMain : Form    {        public FormMain()        {            InitializeComponent();                    }        private List<User> GetUsers(IDataReader reader)        {            var list = new List<User>();            while (reader.Read())            {                list.Add(new User()                {                    ID = reader.GetInt32(reader.GetOrdinal("ID")),                    UserName = reader.GetString(reader.GetOrdinal("UserName")),                    NickName = reader.GetString(reader.GetOrdinal("NickName")),                    Phone = reader.GetString(reader.GetOrdinal("Phone")),                    QQ = reader.GetString(reader.GetOrdinal("QQ")),                });            }            return list;        }        private void btnTest_Click(object sender, EventArgs e)        {            dataGridView1.AutoGenerateColumns = false;            var list = MyDb.LendReader("select * from Users where 0=0", GetUsers);            dataGridView1.DataSource = list;        }    }    public class User    {        public int ID;        public string UserName;        public string NickName;        public string Phone;        public string QQ;    }    public class MyDb    {        public static T LendReader<T>(string sql, BorrowReader<T> borrowReader)        {            using (OleDbConnection connection = CreateConnection())            {                connection.Open();                OleDbCommand c = new OleDbCommand(sql, connection);                OleDbDataReader r = c.ExecuteReader();                return borrowReader(r);            }        }        private static OleDbConnection CreateConnection()        {            string dbName = Path.Combine(Application.StartupPath, "MyData.mdb");            OleDbConnection c = new OleDbConnection            {                ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + dbName            };            return c;        }    }}

二、解决方法

其实很简单，只是很多朋友可能没有考虑到，因为这压根不是什么泛型List或者ArrayList的问题，

只要改代码：

    public class User    {        public int ID;        public string UserName;        public string NickName;        public string Phone;        public string QQ;    }

为：

    public class User    {        public int ID{ get; set; }        public string UserName { get; set; }        public string NickName { get; set; }        public string Phone { get; set; }        public string QQ { get; set; }     }

就好了

三、简单讲解

没定义get、set的是字段，定义了就是属性了，为了安全性考虑，DataGridView 的数据源绑定只能是被公开了的属性，而无权访问字段。很多其他控件也有同样的情况。