vb.net三层实现登录例子

看三层已经很长时间了，中间有经过了期末考试、回家等等琐事，寒假开学的我已经回想不起什么事三层了，经过了三四天的重新复习，再加上查看各期师哥师姐的博客，终于，自己完成了C#视频中的登录小例子，下面就和大家分享一下先：

首先是界面：

这样感觉真心的好看

                                                            

首先我们看一下实体层，也就是图片中的LoginModel      

Public Class Model
    Dim _username As String
    Dim _password As String
    Dim _email As String
    Dim _score As Integer

    Public Property UserName As String   '设置UserName属性
        Get
            Return _username
        End Get
        Set(value As String)
            _username = value
        End Set
    End Property

    Public Property Password As String  '设置Password属性
        Get
            Return _password
        End Get
        Set(value As String)
            _password = value
        End Set
    End Property

    Public Property Email As String
        Get
            Return _email
        End Get
        Set(value As String)
            _email = value
        End Set
    End Property

D层

Public Class UserDAO

    Public conn As New SqlConnection("server=李卫中; database=Login;user id=sa;password=li")
    Public Function SelectUser(ByVal User As Model) As LoginModel.Model
        Dim reader As SqlDataReader
        Dim eUser As New LoginModel.Model

        Dim sql As String = "Select  UserName,Password From Users Where UserName=@UserName And Password=@Password"
        Dim cmd As New SqlCommand(sql, conn)      '创建sqlCommand对象
        cmd.CommandText = sql                     '获取SQL语句的具体内容
        cmd.CommandType = CommandType.Text         '获取上述SQL语句的具体类型，在此为Select
        cmd.Parameters.Add(New SqlParameter("@UserName", User.UserName)) '若用成eUser.UserName则会出现参数未传递的错误提示
        cmd.Parameters.Add(New SqlParameter("@Password", User.Password))

        conn.Open()                                                                                               '打开数据连接
        reader = cmd.ExecuteReader()                     '执行查询语句，并生成一个DataReader

        '读取查询到的数据，并返回给相应的属性
        While reader.Read()
            '获取数据库中相应字段的数据
            '数组必须从零开始读取，否则会超出其界限
            eUser.UserName = reader.GetString(0)
            eUser.Password = reader.GetString(1)
        End While
        Return eUser                                                                                               '返回查询到的实体
        conn.Close()
    End Function

Public Class ScoresDAO                  '这里是实例中的那个登录见证，也就是Score那部分，其实我是照葫芦画瓢，照上面写的
    Public conn As New SqlConnection("server=李卫中; database=Login;user id=sa;password=li")
    Public Function UpdateScore(ByVal User As Model) As LoginModel.Model
        Dim eUser As New LoginModel.Model
        Dim sql As String = "INSERT INTO Scores (UserName,Score) values (@UserName,@Score)"
        Dim cmd As New SqlCommand(sql, conn)      '创建sqlCommand对象
        cmd.CommandText = sql                     '获取SQL语句的具体内容
        cmd.CommandType = CommandType.Text         '获取上述SQL语句的具体类型，在此为Select
        cmd.Parameters.Add(New SqlParameter("@UserName", User.UserName))
        cmd.Parameters.Add(New SqlParameter("@Score", 10))
        conn.Open()

        cmd.ExecuteNonQuery()

        Return eUser                                                                       '返回查询到的实体
        conn.Close()     '视频里讲过，用完了之后，最好是断开连接，省的占用通道               '关闭连接
    End Function

End Class

至于这里，写完之后，看到了慕夏师傅师傅的博客，知道了，应该向C#中一样，讲数据库连接字符串单独提出来，这样，就不用每次都写，见谅

U层：界面层

Public Class frmLogin

  
    Private Sub frmLogin_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        txtUserName.Focus()
        txtUserName.MaxLength = 11             '设置txtUserName 属性
        txtPassword.MaxLength = 10
    End Sub

    Private Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click
        Try

            Dim euser2 As New LoginModel.Model             '实例化新的UserInfo，用来传递B层的实体
            Dim euser3 As LoginModel.Model                    '定义一个类型为UserInfo的参数，用来赋值

            '用户名、密码传入实体层
            euser2.UserName = Trim(txtUserName.Text)
            euser2.Password = txtPassword.Text

            Dim mgr As New LoginBLL.LoginManager
            euser3 = mgr.UserLogin(euser2)
        Catch ex As Exception
            MessageBox.Show(ex.Message.ToString())
        End Try

        
    End Sub

    Private Sub btnCancel_Click(sender As Object, e As EventArgs) Handles btnCancel.Click
        Me.Close()
    End Sub
End Class

B层：业务逻辑层
 

Public Function UserLogin(ByVal User As LoginModel.Model) As LoginModel.Model
        Dim uDao As New LoginDAL.UserDAO
        Dim sDao As New LoginDAL.ScoresDAO
        Dim eUser1 As LoginModel.Model


        eUser1 = uDao.SelectUser(User)


        If IsNothing(eUser1.UserName) Then
            Throw New Exception("密码错误或用户名不存在，登录失败")
        Else
            eUser1 = sDao.UpdateScore(User)


            Return eUser1
        End If
    End Function

自己编点，看看师哥师姐们的博客，结合一下自己以前学到的知识，要知道，所谓的三层其实就是一个解耦的过程，和我们后面遇到的“七层”是一样，用心看看，应该不难

从上面可以看出，我用到的是传实体，之前我问过师傅，到底是传实体好呢，还是传参好呢？（各有各的好处，不同的地方、不同的情况用不同的发放）这是师傅对我说的，虽然我还不能完全掌握使用方法的能力，但是通过练习，我没问题