ADO.NET 【实体类】【数据访问类】

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

namespace ConsoleApplication2.App_Code
{
    public class Users
    {
        private int _Ids;

        public int Ids
        {
            get { return _Ids; }
            set { _Ids = value; }
        }
        private string _UserName;

        public string UserName
        {
            get { return _UserName; }
            set { _UserName = value; }
        }
        private string _PassWord;

        public string PassWord
        {
            get { return _PassWord; }
            set { _PassWord = value; }
        }
        private string _NickName;

        public string NickName
        {
            get { return _NickName; }
            set { _NickName = value; }
        }
        private bool _Sex;

        public bool Sex
        {
            get { return _Sex; }
            set { _Sex = value; }
        }
        private DateTime _Birthday;

        public DateTime Birthday
        {
            get { return _Birthday; }
            set { _Birthday = value; }
        }
        private string _Nation;

        public string Nation
        {
            get { return _Nation; }
            set { _Nation = value; }
        }

    }
}

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

namespace ConsoleApplication2.App_Code
{
    public class UsersData
    {
        SqlConnection conn = null; //“公海” 提升 conn cmd 的作用域
        SqlCommand cmd = null;

        public UsersData()    //构造函数，放置每个方法都要使用，每次实例化都要运行
        {
            string sql = "server=.;database=Data0216;user=sa;pwd=123";

            conn = new SqlConnection(sql);
            cmd = conn.CreateCommand();
        }
        
        //查询所有方法

        public List<Users> SelectAll()    //有返回值 List<Users> 返回一个集合，
        {
            List<Users> list = new List<Users>();  //实例化一个 集合

            cmd.CommandText = "select *from Users";  //查询语句

            conn.Open();

            SqlDataReader dr = cmd.ExecuteReader();

            while (dr.Read())  //在这里没有进行有无 行 的判断，直接读取记录  
            {                                         
                                                   
                Users u = new Users();  //实例化一个 users 对象，前提是已经建立 users 实体类

                u.Ids = Convert.ToInt32(dr["ids"]);
                u.UserName = dr["UserName"].ToString();
                u.PassWord = dr["PassWord"].ToString();
                u.NickName = dr["NickName"].ToString();
                u.Sex = Convert.ToBoolean(dr["Sex"]);
                u.Birthday = Convert.ToDateTime(dr["Birthday"]);
                u.Nation = dr["Nation"].ToString();

                list.Add(u);        
            }
            conn.Close();

            return list;   //返回 list 
        }


        //添加记录方法
        public void Insert(Users u)  //需要输入，输入一个 users 类型的变量
        {
            cmd.CommandText = "insert into Users values(@username,@password,@nickname,@sex,@birthday,@nation)";
            
            cmd.Parameters.Clear();
            cmd.Parameters.AddWithValue("@username", u.UserName);
            cmd.Parameters.AddWithValue("@password", u.PassWord);
            cmd.Parameters.AddWithValue("@nickname", u.NickName);
            cmd.Parameters.AddWithValue("@sex", u.Sex);
            cmd.Parameters.AddWithValue("@birthday", u.Birthday);
            cmd.Parameters.AddWithValue("@nation", u.Nation);

            conn.Open();
            cmd.ExecuteNonQuery();
            conn.Close();
        }

    }
}