三层之常用返回值

我接触三层架构已经有一段时间了,刚开始接触三层架构的时候,有两个问题困扰了我很长时间,第一个是三层应该如何分层呢?第二个问题就是三层返回值如何设置!

提高班的学习方法是项目驱动,后来开始接触用三层写的机房收费系统,对三层也开始慢慢的理解了,慢慢了解了三层的返回值在什么情况下,我该如何返回值,三层架构的返回值一般情况分为以下三种:

一.返回数据表Datatable 或者是数据集Dataset

无论是返回数据集Dataset还是数据表Datatable ,性质都是一样的,使用的情况就是在你需要多条数据的时候,就返回数据表,但是多条数据不放在一个表中,那么这个时候你就可以返回Dataset了,已返回一个数据表为例,我们来看看代码:

D层:

 ''' <summary>
    ''' 值班老师
    ''' </summary>
    Public Function SelectDutyTeacher(ByVal AllThdt As DataTable) As DataTable
        Dim sqlcmdstr As String = "select RecordNo as 记录号,UserName  as 用户名,UseDate  as 登录日期,UseTime as 登录时间 ,RoomNo  as 机器名 from WorkRecord where NouseDate is null"
        Dim table As DataTable
        table = SqlHelp.Sqlhelper.SelectInfo(sqlcmdstr, CommandType.Text)
        Return table
    End Function

B层:

 ''' <summary>
    ''' 正值班教师
    ''' </summary>
    ''' <param name="TeacherInfo"></param>
    ''' <returns>table</returns>
    ''' <remarks>正值班教师表</remarks>
    Public Function DutyTeacher(ByVal TeacherInfo As DataTable) As DataTable
        Dim table As New DataTable
        Dim DalTeacher As New CRCMDAL.DutyTeacherDAL
        '调用D层DutyTeacherDAL类的SelectDutyTeacher方法获取正在值班教师表
        table = DalTeacher.SelectDutyTeacher(table)
        Return table
    End Function

U层:

 Dim BllTeacher As New CRCMBLL.DutyTeacherBLL
        Dim Table As New DataTable

        '先对DataGridView1中的数据进行清除,刷新
        DataGridView1.DataSource = DBNull.Value
        DataGridView1.Refresh()

        '调用B层DutyTeacherBLL类的DutyTeacher方法,获取正在值班教师
        Table = BllTeacher.DutyTeacher(Table)

二.返回实体

我们都知道,三层的传值是通过实体传递的,因为实体遵从了面向对象设计的开闭原则,如果你的程序集中,返回的值有且仅有一条记录的时候,你就可以返回实体了,这样就比较方便,

界面:

D层:

''' <summary>
    ''' 通过卡号查找相关信息
    ''' </summary>
    ''' <param name="StudentInfo"></param>
    ''' <returns>EntityStudent</returns>
    ''' <remarks>返回学生的基本信息实体</remarks>
    Public Function selectStudent(ByVal StudentInfo As StudentBasicInfoEntity) As StudentBasicInfoEntity


        Dim EntityStudent As New CRCMEntity.StudentBasicInfoEntity
        Dim sqlcmdstr As String = "select *  from StudentBasicInfo where StudentCardID =@StudentCardID"
        Dim paras As SqlParameter() = {New SqlParameter("@StudentCardID", StudentInfo.StudentCardID)}
        Dim table As DataTable
        table = SqlHelp.Sqlhelper.SelectInfo(sqlcmdstr, CommandType.Text, paras)


        EntityStudent.StudentCardID = table.Rows(0).Item("StudentCardID")
        EntityStudent.StudentID = table.Rows(0).Item("StudentID")
        EntityStudent.StudentName = table.Rows(0).Item("StudentName")
        EntityStudent.StudentSex = table.Rows(0).Item("StudentSex")
        EntityStudent.Department = table.Rows(0).Item("Department")
        EntityStudent.Studenttype = table.Rows(0).Item("Studenttype")
        EntityStudent.Cash = table.Rows(0).Item("Cash")
        EntityStudent.Grade = table.Rows(0).Item("Grade")
        EntityStudent.ClassNo = table.Rows(0).Item("ClassNo")
        EntityStudent.Marks = table.Rows(0).Item("Marks")


        Return EntityStudent
    End Function

B层:

 

''' <summary>
    ''' 查找学生的基本信息
    ''' </summary>
    ''' <param name="StudentInfo"></param>
    ''' <returns>EntityStudent</returns>
    ''' <remarks>学生基本信息实体</remarks>
    Public Function SelectStudentInfo(ByVal StudentInfo As StudentBasicInfoEntity) As StudentBasicInfoEntity
        Dim EntityStudent As New CRCMEntity.StudentBasicInfoEntity
        Dim DalStudent As New CRCMDAL.ModifyStudentInfoDAL

        EntityStudent.StudentCardID = StudentInfo.StudentCardID
        EntityStudent = DalStudent.selectStudent(EntityStudent)
        Return EntityStudent

U层:

''' <summary>
    '''显示学生基本信息
    ''' </summary>
    Public Function ShowStudentInfo() As Boolean
        Dim EntityStudent As New CRCMEntity.StudentBasicInfoEntity
        Dim BllStudent As New CRCMBLL.ModifyStudentBll

        txtStudentCardID.Text = FrmStuBasicModify.StudentCardID

        '卡号
        EntityStudent.StudentCardID = txtStudentCardID.Text

        '调用B层的SelectStudentInfo方法获取全部学生信息
        EntityStudent = BllStudent.SelectStudentInfo(EntityStudent)

        txtStudentCardID.Text = EntityStudent.StudentCardID
        '学号
        txtStudentID.Text = EntityStudent.StudentID
        '性别
        txtStudentSex.Text = EntityStudent.StudentSex
        '姓名
        txtStudentName.Text = EntityStudent.StudentName
        '系别
        txtDepartment.Text = EntityStudent.Department
        '年级
        txtGrade.Text = EntityStudent.Grade
        '班级
        txtClassNo.Text = EntityStudent.ClassNo
        '金额
        txtCash.Text = EntityStudent.Cash
        '卡类型
        txtStudenttype.Text = EntityStudent.Studenttype
        '备注
        txtMarks.Text = EntityStudent.Marks

        Return True
    End Function

三.返回Boolen

当我们对数据进行增,删,改的时候,对执行ExecuteNonQuery命令, ExecuteNonQuery返回的是行数,就可以更加ExecuteNonQuery返回行数判断是否对数据库表的增,删,改是否成功了!

界面:

D层:

 ''' <summary>
    ''' 更改学生的基本信息
    ''' </summary>
    ''' <param name="StudentInfo"></param>
    ''' <returns>Boolean</returns>
    ''' <remarks>修改成功返回True,不成功返回false</remarks>
    Public Function InsertStudent(ByVal StudentInfo As StudentBasicInfoEntity) As Boolean
        'Dim EntityStudent As New CRCMEntity.StudentBasicInfoEntity
        Dim sqlcmdstr As String = "PROC_CR_ModifyStudentBasic"
        Dim paras As SqlParameter() = {New SqlParameter("@StudentCardID", StudentInfo.StudentCardID),
                                       New SqlParameter("@StudentID", StudentInfo.StudentID),
                                     New SqlParameter("@StudentName", StudentInfo.StudentName),
                                     New SqlParameter("@StudentSex", StudentInfo.StudentSex),
                                     New SqlParameter("@Department", StudentInfo.Department),
                                     New SqlParameter("@Grade", StudentInfo.Grade),
                                     New SqlParameter("@ClassNo", StudentInfo.ClassNo),
                                     New SqlParameter("@Marks", StudentInfo.Marks)
                                    }
        Dim res As Integer  '定义受影响的行数
        res = SqlHelp.Sqlhelper.ExecuteNoQuery(CommandType.StoredProcedure, sqlcmdstr, paras)

        '返回收影响的行数为-1,则返回true,反之返回False
        If res < 0 Then
            Return True
        Else
            Return False
        End If
    End Function

B层:

    ''' <summary>
    ''' 把修改的学生基本信息插入数据库表中
    ''' </summary>
    ''' <param name="StudentInfo"></param>
    ''' <returns>Boolean</returns>
    ''' <remarks>更新成功返回True,不成功返回False</remarks>
    Public Function InsertStudent(ByVal StudentInfo As StudentBasicInfoEntity) As Boolean

        Dim DalStudent As New CRCMDAL.ModifyStudentInfoDAL

        '判断是否更新成功,若更新成功返回True,反之返回false
        If DalStudent.InsertStudent(StudentInfo) Then
            Return True
        Else
            Return False
        End If
    End Function

U层:

    ''' <summary>
    '''确定修改
    ''' </summary>
    Private Sub btnModify_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnModify.Click
        Dim EntityStudent As New CRCMEntity.StudentBasicInfoEntity
        Dim BllStudent As New CRCMBLL.ModifyStudentBll

        '卡号
        EntityStudent.StudentCardID = txtStudentCardID.Text
        '学号
        EntityStudent.StudentID = txtStudentID.Text
        '性别
        EntityStudent.StudentSex = txtStudentSex.Text
        '姓名
        EntityStudent.StudentName = txtStudentName.Text
        '系别
        EntityStudent.Department = txtDepartment.Text
        '年级
        EntityStudent.Grade = txtGrade.Text
        '班级
        EntityStudent.ClassNo = txtClassNo.Text
        '备注
        EntityStudent.Marks = txtMarks.Text

        '调用B层的InsertStudent方法,插入修改信息
        If BllStudent.InsertStudent(EntityStudent) Then
            MsgBox("修改成功!", vbOK, "温馨提示")
        End If
    End Sub

在做机房收费系统的时候,和进度差不多的人交流了一下,也有些人比较喜欢倾向于返回的值全部是datatable或者是dataset,在B层或C层需要的时候再取,在进行值的比较处理,无论你用那种返回值,都是没有错误的,但是根据不同的情况,返回不同的值,就会相对的提高我们的效率!