三层架构下实现用户登陆C#

   上篇文章讲到三层。接下来就通过一个实例详细的看怎么用三层实现用户登陆界面。

  一、Model实体（LoginModel）:
         

namespace LoginModel
{
     //加入类:UserInfo  Model实体作用：封装数据，使数据在三层中传输 。更倾向于业务逻辑层
    public class UserInfo
    {
        //定义用户属性
        public int ID { get; set; }
        public string UserName { get; set; }
        public string Password { get; set; }
        
    }
}

 首先简单的界面相信大家都会：

接下来是代码：

namespace LoginUI
{
    public partial class frmLogin : Form
    {
        public frmLogin()
        {
            InitializeComponent();
        }
        private void btnLogin_Click(object sender, EventArgs e)
        {
            //UI层将用户输入数据传递给BLL层
            string userName = txtUserName.Text.Trim();
            string password = txtPassword.Text;
            LoginBLL.LoginManager mgr = new LoginBLL.LoginManager();
            LoginModel.UserInfo user = mgr.UserLogin(userName, password);

            //将UI层返回业务层传递的数据给用户
            MessageBox.Show("登陆用户：" + user.UserName);
        }       
    }
}

namespace LoginBLL
{
    public class LoginManager
    {
        public LoginModel.UserInfo UserLogin(string userName, string password)
        {
            LoginDAL.UserDAO uDao = new LoginDAL.UserDAO();//实例化DAL层
            LoginModel.UserInfo user = uDao.SelectUser(userName, password);

            //不需訪问数据源直接运行业务逻辑
            if (user != null)
            {
                return user;
            }
            else
            {
                throw new Exception("登陆失败");                
            }
        }
    }
}

 public class UserDAO
    {
        public LoginModel.UserInfo SelectUser(string userName, string Password)
        {
            
            //建立数据库连接
            string ConnString = @"Server=192.168.24.154;DataBase=机房收费系统人员记录; User ID=sa; Password=123";
            using (SqlConnection conn = new SqlConnection(ConnString))
            {
                //运行SQL语句进行查询
                SqlCommand cmd = conn.CreateCommand();
                cmd.CommandText = @"SELECT ID,UserName,Password FROM UserInfo WHERE UserName=@UserName AND Password=@Password";
                //输出查询结果
                cmd.CommandType = CommandType.Text;

                //加入两个參数
                cmd.Parameters.Add(new SqlParameter(@"UserName", userName));
                cmd.Parameters.Add(new SqlParameter(@"Password", Password));

                conn.Open();
                SqlDataReader reader = cmd.ExecuteReader();

                LoginModel.UserInfo user = null;

                //读取详细的数据
                while (reader.Read())
                {
                    if (user == null)
                    {
                        user = new LoginModel.UserInfo();
                    }
                    //读取查询到的数据
                    user.ID = reader.GetInt32(0);
                    user.UserName = reader.GetString(1);
                    user.Password = reader.GetString(2);
                   
                }
                return user;
            }
        }
    }
}

结果显示：