数据增删改查之三层架构（理解三层续）

首先是画的图，感觉把图画完了，工程就完成了一大半，前提是画的思路是对的。还是在理解三层。

下面是画的关于数据的增删改查这个小例子的包图、类图和时序图。

包图。

类图。

时序图。

用户注册。

用户删除。

用户查询，一个是查选全部用户，一个是查询一个用户对象。

用户修改。也就是查询、删除和增加。

用户注册的代码，如下所示：

实体层代码。

Public Class UserInfo Private userID As Integer Private userName As String Private userActor As String Private userPwd As String Private userRegDate As DateTime Private userFlag As Boolean '用户编号属性 Public Property UserID() As Integer Get Return userID End Get Set(ByVal value As Integer) userID = value End Set End Property '用户姓名属性 Public Property UserName() As String Get Return userName End Get Set(ByVal value As String) userName = value End Set End Property '用户角色 Public Property UserActor() As String Get Return userActor End Get Set(ByVal value As String) userActor = value End Set End Property '用户密码 Public Property UserPwd() As String Get Return userPwd End Get Set(ByVal value As String) userPwd = value End Set End Property '用户注册日期 Public Property UserRegDate() As DateTime Get Return userRegDate End Get Set(ByVal value As DateTime) userRegDate = value End Set End Property '用户合法标致 Public Property UserFlag Get Return userFlag End Get Set(ByVal value) userFlag = value End Set End Property End Class

DAL层代码。

Imports System.Data.SqlClient 'DAL包中的DALuser类。 Public Class DALUser '数据库连接字符串 Dim connStr As String = "Data Source=192.168.24.63;Initial Catalog=PCharge_Sys;User ID=sa;Password=sa" ''' <summary> ''' 添加一条用户信息 ''' </summary> ''' <param name="EntityUserInfo">一个用户对象</param> ''' <returns>是否添加成功</returns> ''' <remarks>2012年1月19号 20：31</remarks> Public Function DALUserAdd(ByVal EntityUserInfo As Entity.UserInfo) As Boolean Dim sql As String = "Insert into UserInfo(UserID,UserName,UserActor,UserPwd,UserRegDate,UserFlag)" _ & " values (@UserID,@UserName,@UserActor,@UserPwd,@UserRegDate,@UserFlag) " Dim conn As SqlConnection = New SqlConnection(connStr) Dim cmd As SqlCommand = New SqlCommand(sql, conn) Dim sqlParam As New SqlParameter sqlParam = New SqlParameter("@UserID", SqlDbType.Int) sqlParam.Value = EntityUserInfo.UserID cmd.Parameters.Add(sqlParam) sqlParam = New SqlParameter("@UserName", SqlDbType.VarChar) sqlParam.Value = EntityUserInfo.UserName cmd.Parameters.Add(sqlParam) sqlParam = New SqlParameter("@UserActor", SqlDbType.VarChar) sqlParam.Value = EntityUserInfo.UserActor cmd.Parameters.Add(sqlParam) sqlParam = New SqlParameter("@UserPwd", SqlDbType.VarChar) sqlParam.Value = EntityUserInfo.UserPwd cmd.Parameters.Add(sqlParam) sqlParam = New SqlParameter("@UserRegDate", SqlDbType.DateTime) sqlParam.Value = EntityUserInfo.UserRegDate cmd.Parameters.Add(sqlParam) sqlParam = New SqlParameter("@UserFlag", SqlDbType.Bit) sqlParam.Value = EntityUserInfo.UserFlag cmd.Parameters.Add(sqlParam) Try conn.Open() Return cmd.ExecuteNonQuery() > 0 Catch ex As Exception Return False End Try If Not IsNothing(conn) Then conn.Close() conn = Nothing End If End Function End Class

BLL层代码。

Imports DAL ''' <summary> ''' BLL包中的BLLUser类。 ''' </summary> ''' <remarks></remarks> Public Class BLLUser ''' <summary> ''' 插入一条用户信息 ''' </summary> ''' <param name="EntityUserInfo"></param> ''' <returns></returns> ''' <remarks></remarks> Public Function BLLUserAdd(ByVal EntityUserInfo As Entity.UserInfo) As Boolean Dim DALUserInfo As New DAL.DALUser Return DALUserInfo.DALUserAdd(EntityUserInfo) End Function End Class

UI层代码。

界面层。

'界面层。 Public Class UserAddForm ''' <summary> ''' 用户注册，并对用户的输入加以判断。 ''' </summary> ''' <param name="sender"></param> ''' <param name="e"></param> ''' <remarks></remarks> Private Sub RegisterBut_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RegisterBut.Click If txtUserID.Text = "" Or txtUserName.Text = "" Or txtUserPwd.Text = "" Or txtUserRegDate.Text = "" Or txtUserActor.Text = "" Or txtUserFlag.Text = "" Then MsgBox("输入不能为空！请重新输入！") Else If Not IsNumeric(txtUserID.Text) Then MsgBox("输入的编号因为数字！请重新输入！") End If If Not IsDate(txtUserRegDate.Text) Then MsgBox("输入的注册日期请为日期XXXX-XX-XX格式!") Else Dim EntityUserInfo As New Entity.UserInfo EntityUserInfo.UserID = txtUserID.Text EntityUserInfo.UserName = txtUserName.Text EntityUserInfo.UserActor = txtUserActor.Text EntityUserInfo.UserPwd = txtUserPwd.Text EntityUserInfo.UserRegDate = txtUserRegDate.Text EntityUserInfo.UserFlag = txtUserFlag.Text Dim BLLUserInfo As New BLL.BLLUser If BLLUserInfo.BLLUserAdd(EntityUserInfo) Then MsgBox("添加成功！") Else MsgBox("添加失败！") End If End If End If End Sub End Class

上面是在数据库表中插入一条记录，其他的删除和修改，查询类似，就是DAL和BLL层返回值可能不同。

DAL层删除查询代码，保存备后用。

''' <summary> ''' 获得所有用户 ''' </summary> ''' <returns>所有用户的DataSet集合</returns> ''' <remarks></remarks> Public Function DALUserSelectAll() As DataSet Dim sql As String = "select * from UserInfo" Dim conn As SqlConnection = New SqlConnection(connStr) Dim cmd As SqlCommand = New SqlCommand(sql, conn) Dim dap As SqlDataAdapter = New SqlDataAdapter(cmd) Dim ds As New DataSet Try conn.Open() dap.Fill(ds) Return ds Catch ex As Exception Return Nothing Finally If Not IsNothing(cmd) Then cmd.Dispose() cmd = Nothing End If If Not IsNothing(conn) Then conn.Close() conn = Nothing End If End Try End Function ''' <summary> ''' 获得一个用户的信息。 ''' </summary> ''' <param name="UserID"></param> ''' <returns>一个用户的对象</returns> ''' <remarks></remarks> Public Function DALUserGetObject(ByVal UserID As Integer) As Entity.UserInfo Dim sql As String = "select UserName,UserActor,UserPwd,UserRegDate,UserFlag from UserInfo where [email protected]" Dim conn As SqlConnection = New SqlConnection(connStr) Dim cmd As SqlCommand = New SqlCommand(sql, conn) Dim sqlParam As New SqlParameter("@UserID", SqlDbType.Int) sqlParam.Value = UserID Dim sdr As SqlDataReader = Nothing Dim DALEntityUserinfo As New Entity.UserInfo Try sdr = cmd.ExecuteReader() While sdr.Read DALEntityUserinfo.UserID = UserID DALEntityUserinfo.UserName = sdr.GetString(0) DALEntityUserinfo.UserActor = sdr.GetString(1) DALEntityUserinfo.UserPwd = sdr.GetString(2) DALEntityUserinfo.UserRegDate = sdr.GetString(3) DALEntityUserinfo.UserFlag = sdr.GetString(4) End While Return DALEntityUserinfo Catch ex As Exception Return Nothing Finally If Not IsNothing(sdr) Then sdr.Close() sdr = Nothing End If If Not IsNothing(cmd) Then cmd.Dispose() cmd = Nothing End If If Not IsNothing(conn) Then conn.Close() conn = Nothing End If End Try End Function Public Function DALUserDel(ByVal DALEntityUserinfo As Entity.UserInfo) As Boolean Dim sql As String = "delete from UserInfo where [email protected]" Dim conn As SqlConnection = New SqlConnection(connStr) Dim cmd As SqlCommand = New SqlCommand(sql, conn) Dim sqlParam As New SqlParameter("@UserID", SqlDbType.Int) sqlParam.Value = DALEntityUserinfo.UserID Try conn.Open() Return cmd.ExecuteNonQuery() > 0 Catch ex As Exception Return False Finally If Not IsNothing(cmd) Then cmd.Dispose() cmd = Nothing End If If Not IsNothing(conn) Then conn.Close() conn = Nothing End If End Try End Function End Class

以上只是为了理解而理解，所以做小例子，可能有很多缺陷，欢迎您指教。