【C#】实战篇－Ｃ＃版登录

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三层只是分层的一种经典形式，具体分几层，分情况而定。在学习阶段，我们一般用三层架构，分别是ＵＩ层、ＢＬＬ层、ＤＡＬ层，另外我们常用一个Ｍｏｄｅｌ来封装我们需要的数据；在开发阶段，会有四层到七层。下面用一个小实例更深层次的理解三层。

一、各层的调用关系

二、构建三层框架并添加相应的引用

三、数据库设计

四、代码实现

【UI层】

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;namespace LoginUI
{public partial class Form1 : Form{public Form1(){InitializeComponent();//初始化}private void btnLogin_Click(object sender, EventArgs e){//获取数据string userName = txtUserName.Text.Trim();string password = txtPassword.Text;Login.BLL.LoginManager mgr = new Login.BLL.LoginManager();//定义一个业务逻辑类Login .Model .UserInfo user= mgr.UserLogin(userName, password);MessageBox.Show("登录用户：" + user.UserName);}private void btnNo_Click(object sender, EventArgs e){Application.Exit();}}
}

【BLL层】－LoginManager

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace Login.BLL
{public class LoginManager{public Login.Model .UserInfo  UserLogin(string userName,string password)//返回UserInfo{Login.DAL.UserDAO uDao = new Login.DAL.UserDAO();//呼叫数据源Login.Model.UserInfo user= uDao.SelectUser(userName, password);//查询并返回user（包括用户名和密码）//判断用户名和密码if (user!=null )//登录成功{Login.DAL.ScoreDAO sDao = new Login.DAL.ScoreDAO();sDao.UpdateScore(userName, 10);//更新Score表return user;}else{throw new Exception("登录失败");}}}
}

【DAL层】－UserDAO

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.SqlClient;namespace Login.DAL
{public class UserDAO//验证用户名和密码的业务{public Login .Model .UserInfo  SelectUser(string userName,string password){using ( SqlConnection conn=new SqlConnection (DbUtil .ConnString )){//执行SQL语句进行查询SqlCommand cmd = conn.CreateCommand();cmd.CommandText = @"SELECT ID,UserName,Password,Email FROM USERS WHERE UserName=@UserName AND PassWord =@PassWord";//添加两个参数cmd.Parameters.Add(new SqlParameter("@UserName", userName));cmd.Parameters.Add(new SqlParameter("@Password", password));//输出查询结果cmd.CommandType = CommandType.Text;conn.Open();SqlDataReader reader = cmd.ExecuteReader();Login.Model.UserInfo user = null;//读取具体的数据while(reader.Read ()){if(user==null){user = new Login.Model.UserInfo();}//读取查询到的数据user.ID = reader.GetInt32(0);user.UserName = reader.GetString(1);user.Password = reader.GetString(2);if(!reader .IsDBNull (3)){user.Email = reader.GetString(3);}}return user;}}}
}

【DAL层】－ScoreDAO

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.SqlClient;namespace Login.DAL
{public  class ScoreDAO{public void UpdateScore(string userName,int value){using (SqlConnection conn=new SqlConnection (DbUtil .ConnString )){SqlCommand cmd = conn.CreateCommand();      //实例化命令对象cmd.CommandText = @"INSERT INTO SCORES(UserName,Score) Values (@UserName,@Score)";//给命令对象添加参数cmd.Parameters.Add(new SqlParameter("@UserName", userName));cmd.Parameters.Add(new SqlParameter("@Score", value));conn.Open();             cmd.ExecuteNonQuery();      //返回受影响的行数。}}}
}

【DAL层】－Dbutil

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace Login.DAL
{class DbUtil{//建立数据库本地连接public static string ConnString = @"Server=咩咩;Database=Login;User ID=sa;Password=123456";}
}

【Model层】－UserInfo

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace Login.Model
{//封装数据，供三层调用;更偏向业务逻辑层public class UserInfo{//定义用户的属性public int ID { get; set; }public string UserName { get; set; }public string Password { get; set; }public string Email { get; set; }}
}

五、运行效果