VB.NET版三层登录小例子

<span style="font-size:24px;">Public Class UserInfo
    Dim _username As String
    Dim _password As String
    Dim _email As String
    Public Property UserName() As String
        Get
            Return _username
        End Get
        Set(value As String)
            _username = value
        End Set
    End Property
    Public Property Password As String
        Get
            Return _password
        End Get
        Set(value As String)
            _password = value
        End Set
    End Property
    Public Property Exmail() As String
        Get
            Return _email
        End Get
        Set(value As String)
            _email = value
        End Set
    End Property
End Class
</span>

<span style="font-size:24px;"></span><pre name="code" class="vb">Public Class Scores
    Dim _score As String
    Public Property Scores() As String
        Get
            Return _score
        End Get
        Set(value As String)
            _score = value
        End Set
    End Property
End Class

Public Class Form1
    Private Sub btOk_Click(sender As Object, e As EventArgs) Handles btOk.Click
        Dim manager As BLL.LoginManager = New BLL.LoginManager()
        Dim user As Model.UserInfo = New Model.UserInfo()
        user.UserName = txtUserName.Text    '通过文本框给User实体赋值
        user.Password = txtPassword.Text
        manager.UserLogin(user)      'user作为实体参数传给B层
        MessageBox.Show("成功登录：" + user.UserName)
    End Sub
End Class

Public Class LoginManager
    Public Function UserLogin(ByVal user As Model.UserInfo) As Model.UserInfo
        Dim userD As DAL.UserDAO = New DAL.UserDAO()
        Dim Uuser As Model.UserInfo = New Model.UserInfo()
        Dim score As Model.Scores = New Model.Scores()
        Uuser = userD.SelectUser(user)   'user作为实体传给D层，但是Uuser中还没有值（正向）
        'Uuser变量是从数据库中查询完毕后从D层传回来的数据
        If (Not IsDBNull(Uuser)) Then
            score.Scores = 20  '给score变量的Scores属性赋值
            Dim sc As DAL.ScoreDAO = New DAL.ScoreDAO()
            sc.UpdateScore(Uuser, score) '将两个实体作为参数再次传给D层
        Else
            Throw New Exception("登录失败")
        End If
        Return Uuser
    End Function
End Class

Imports System.Data.SqlClient
Public Class DbUtil
    Public Shared Function ConnString() As SqlConnection
        Dim cnStr As String = "Server =晓;DataBase =Login;User ID=sa;Password=123456"
        Dim cn As SqlConnection = New SqlConnection(cnStr)
        Return cn
    End Function
End Class

</pre><pre name="code" class="vb">Imports System.Data.SqlClient
Public Class ScoreDAO
    Public Sub UpdateScore(ByVal user As Model.UserInfo, ByVal score As Model.Scores)
        Dim cn As SqlConnection = DbUtil.ConnString() '连接数据库
        Dim sql As String = "INSERT INTO SCORES(UserName,Score) Values(@UserName,@Score)"
        Dim cmd As SqlCommand = New SqlCommand(sql, cn) '执行SQL语句
        '给占位符赋值
        cmd.Parameters.Add(New SqlParameter("@UserName", user.UserName))
        cmd.Parameters.Add(New SqlParameter("@Score", score.Scores))
        cn.Open() '打开数据库
        cmd.ExecuteNonQuery()
    End Sub
End Class

Imports System.Data.SqlClient
Public Class UserDAO
    Public Function SelectUser(ByVal user As Model.UserInfo) As Model.UserInfo
        Dim cn As SqlConnection = DbUtil.ConnString()
        Dim sql As String = "SELECT ID,UserName,Password,Email FROM USERS WHERE UserName =@UserName AND Password = @Password"
        Dim cmd As SqlCommand = New SqlCommand(sql, cn)
        cmd.Parameters.Add(New SqlParameter("@UserName", user.UserName))
        cmd.Parameters.Add(New SqlParameter("@Password", user.Password))
        cn.Open()
        Dim reader As SqlDataReader = cmd.ExecuteReader()
        Dim Buser As Model.UserInfo = New Model.UserInfo()  '实例化Buser往B层传参
        While (reader.Read())
            Buser.UserName = reader.GetString(1)
            Buser.Password = reader.GetString(2)
        End While
        Return Buser
    End Function
End Class