三层与MVC

最新推荐文章于 2022-03-28 12:26:31 发布

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三层：

用图做说明：

MVC：

用图做说明：

三层与MVC联系：

用图做说明：

三层与MVC区别：

第一：三层是一个分层式的软件体系架构设计；MVC是一种框架模式，强制性将应用程序的输入、处理、输出分开，是一种解决方案。

第二：三层适用于任何一个项目，MVC有选择性的使用，且主要使用在WEB页面上

第三：三层基于业务的逻辑来分；MVC基于页面来分。

第四：三层目的重点是高内聚，低耦合，即解耦；MVC目的重点是实现WEB系统的职能划分，也是解耦。

第五：三层不一定就是三层，也有可能是二层，乃至多层；MVC却总是三层

三层实例：

上面是对三层和MVC简单的一个理解，由于现在侧重点不是MVC，而是三层，所以也就没有做有关MVC的例子，对于MVC怎样也不了解。

层次展示：

窗体界面：

Common类：

与数据相关，与工程无关。

Imports System.Data.SqlClient
Public Class CDataBase

    '要连接的数据库连接字符串
    Public Shared Function strConnection() As String
        strConnection = "data source=192.168.24.83;initial catalog=charge_sys;user id=sa;password=123456;"
    End Function
 Public Shared Function ExecQuery(ByVal strSql As String) As SqlClient.SqlDataReader
        Dim Coon As New SqlClient.SqlConnection
        Dim cmd As New SqlClient.SqlCommand
        Dim Reader As SqlClient.SqlDataReader

        '数据库连接
        Coon = New SqlClient.SqlConnection(CDataBase.strConnection())
        cmd.Connection = Coon
        cmd.CommandText = strSql
        cmd.CommandType = CommandType.Text

        Try
            Coon.Open()
            '查询
            Reader = cmd.ExecuteReader()
            '读取字段
        Catch ex As Exception
            MsgBox(ex.Message())
        End Try
        Return Reader
        Coon.Close()
    End Function
End Class

DAL层：

根据权限找到适合自己的SQL语句，通过Common类访问数据库，读取相应数据资料。

Imports System.Data.SqlClient
Public Class DabaBase
    Function SeletUser(ByVal leavel As Modal.Muser) As List(Of Modal.Muser)
        Dim strSql As String
        Dim reader As SqlClient.SqlDataReader
        Dim common = New Common.CDataBase
        Dim UserLeavel As Modal.Muser
        Dim Dlist As New List(Of Modal.Muser)
        Dim Query As String

        Query = leavel.level '获取传过来的leavel字段
        Select Case Query
            Case "管理员"
                strSql = "select * from User_Info	where Level ='管理员'"
            Case " 操作员"
                strSql = "select * from User_Info where Level ='操作员'"
            Case "一般用户"
                strSql = "select * from User_Info where Level ='一般用户'"
        End Select
        '查询
        reader = common.ExecQuery(strSql)
        Try
            While reader.Read()
                UserLeavel = New Modal.Muser
                UserLeavel.userID = reader.GetString(0).Trim
                UserLeavel.PWD = reader.GetString(1).Trim
                UserLeavel.level = reader.GetString(2).Trim
                UserLeavel.UserName = reader.GetString(3).Trim
                UserLeavel.Head = reader.GetString(4).Trim
                Dlist.Add(UserLeavel)
            End While
        Catch ex As Exception
            MsgBox(ex.Message())   '获取异常
        End Try
        Return Dlist
    End Function
End Class

Modal类：

借助Modal传参，将UL层的参数传入DAL层，获得查询语句，同时又将获得的查询结果返回，传回UI层。

Public Class Muser
    Private _userID As String
    Public Property userID As String
        Get
            Return _userID
        End Get
        Set(ByVal value As String)
            _userID = value
        End Set
    End Property
    Private _PWD As String
    Public Property PWD As String
        Get
            Return _PWD
        End Get
        Set(ByVal value As String)
            _PWD = value
        End Set
    End Property
    Private _Level As String
    Public Property level As String
        Get
            Return _Level
        End Get
        Set(ByVal value As String)
            _Level = value
        End Set
    End Property
    Private _UserName As String
    Public Property UserName As String
        Get
            Return _UserName
        End Get
        Set(ByVal value As String)
            _UserName = value
        End Set
    End Property
    Private _Head As String
    Public Property Head As String
        Get
            Return _Head
        End Get
        Set(ByVal value As String)
            _Head = value
        End Set
    End Property
End Class

BLL层：

BLL层，进行各种逻辑判断，将获取字段通过参数传到DAL层，同时又将结果返回。

Public Class BJudge
    Function GetUser(ByVal leavel As Modal.Muser) As List(Of Modal.Muser)
        Dim selectuser As New List(Of Modal.Muser)  '初始化
        Dim LDal As New DataBase.DabaBase           '初始化

        '传参（获取字段和查询结果）
        selectuser = LDal.SeletUser(leavel)
        Return LDal.SeletUser(leavel)
    End Function
End Class

UI层：

接受数据，显示数据等，这里接受字段名，通过查询后，将结果显示。

Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        '下拉框中显示字段
        cmbSelect.Items.Add("管理员")
        cmbSelect.Items.Add("一般用户")
        cmbSelect.Items.Add("操作员")
    End Sub
    Private Sub cmbSelect_SelectedValueChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbSelect.SelectedValueChanged
        Dim sourse As New BLL.BJudge
        Dim users As New Modal.Muser
        users.level = cmbSelect.SelectedItem()  '选择的字段给users
        DataGridView1.DataSource = sourse.GetUser(users)
    End Sub
End Class