机房重构—组合查询&模板方法

       设计模式虽然学了一遍，但也仅限于纸上谈兵，在机房重构中还是不知道如何去用，而且感觉刻意去套模式还麻烦，但是使用模板方法的好处确是实实在在，显而易见的啊，既大大减少了代码量还省去了绘制窗体界面的麻烦，给一个大大的赞~~

       模板方法

      先是定义一个顶级算法的骨架，将代码提炼，而将一些步骤延迟到子类；而子类可重定义算法的某些步骤，实现父类所定义的抽象方法。

        

       组合查询

      1、建立模板父窗体

 '实例化组合查询的实体    Protected GroupInquire As New Model.GroupInquireInfo    Private Sub frmGroupParent_Load(sender As Object, e As EventArgs) Handles MyBase.Load        '将参数传递给实体，赋初值        '字段名        GroupInquire.CmbName1 = ""        GroupInquire.CmbName2 = ""        GroupInquire.CmbName3 = ""        '操作符        CmbMark1.Items.Add(">")        CmbMark1.Items.Add("<")        CmbMark1.Items.Add("=")        CmbMark1.Items.Add("<>")        CmbMark2.Items.Add(">")        CmbMark2.Items.Add("<")        CmbMark2.Items.Add("=")        CmbMark2.Items.Add("<>")        CmbMark3.Items.Add(">")        CmbMark3.Items.Add("<")        CmbMark3.Items.Add("=")        CmbMark3.Items.Add("<>")        '关系        CmbRelation1.Items.Add("与")        CmbRelation1.Items.Add("或")        CmbRelation2.Items.Add("与")        CmbRelation2.Items.Add("或")        CmbName2.Enabled = False        CmbName3.Enabled = False        CmbMark2.Enabled = False        CmbMark3.Enabled = False        CmbRelation2.Enabled = False        txtContent2.Enabled = False        txtContent3.Enabled = False        Dim i As Integer        For i = 0 To dgv.Columns.Count - 1            dgv.Columns(i).Width = DataGridViewAutoSizeColumnMode.AllCells        Next    End Sub    '查询    Private Sub btnQuery_Click(sender As Object, e As EventArgs) Handles btnQuery.Click        If CmbRelation1.Text = "" Then            If CmbName1.Text = "" Or CmbMark1.Text = "" Or txtContent1.Text = "" Then                MsgBox("第一行查询条件不能为空，请完善", , "提示")                Exit Sub            End If        End If        If CmbRelation1.Text <> "" Then            If CmbName1.Text = "" Or CmbMark1.Text = "" Or txtContent1.Text = "" Or CmbName2.Text = "" Or CmbMark2.Text = "" Or txtContent2.Text = "" Then                MsgBox("所输入的查询条件不能为空，请完善", , "提示")                Exit Sub            End If        End If        If CmbRelation2.Text <> "" Then            If CmbName1.Text = "" Or CmbMark1.Text = "" Or txtContent1.Text = "" Or CmbName2.Text = "" Or CmbMark2.Text = "" Or txtContent2.Text = "" Or CmbName3.Text = "" Or CmbMark3.Text = "" Or txtContent3.Text = "" Then                MsgBox("所输入的查询条件不能为空，请完善", , "提示")                Exit Sub            End If        End If        '将参数传给实体        GroupInquire.DbName = GetdbName()        GroupInquire.CmbName1 = GetEnglish(CmbName1.Text)        GroupInquire.CmbName2 = GetEnglish(CmbName2.Text)        GroupInquire.CmbName3 = GetEnglish(CmbName3.Text)        GroupInquire.CmbMark1 = CmbMark1.Text.Trim        GroupInquire.CmbMark2 = CmbMark2.Text.Trim        GroupInquire.CmbMark3 = CmbMark3.Text.Trim        GroupInquire.TxtContent1 = txtContent1.Text.Trim        GroupInquire.TxtContent2 = txtContent2.Text.Trim        GroupInquire.TxtContent3 = txtContent3.Text.Trim        GroupInquire.CmbRelation1 = GetEnglish(CmbRelation1.Text)        GroupInquire.CmbRelation2 = GetEnglish(CmbRelation2.Text)        Dim dt As New DataTable        Dim Generalfacade As New Facade.GeneralFacade  '实例化外观层        dt = Generalfacade.FGroupCheck(GroupInquire)        If (dt.Rows.Count = 0) Then            MsgBox("没有符合条件的记录", , "提示")            Exit Sub        Else            Call Todgv(GroupInquire)  '把表显示到datagridview中         End If    End Sub    '模板方法，定义虚函数GetEnglish，查询字段转化为数据库字段     Public Overridable Function GetEnglish(cmbName As String) As String        Return ""    End Function    '获得数据库表名      Protected Overridable Function GetdbName() As String        Return ""    End Function    '把表显示到datagridview中    Protected Overridable Sub Todgv(ByVal comQueryEntity As GroupInquireInfo)    End Sub    '第一个组合关系是否为空    Private Sub CmbRelation1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles CmbRelation1.SelectedIndexChanged        If CmbRelation1.Text = "" Then            CmbName2.Enabled = False            CmbName3.Enabled = False            CmbMark2.Enabled = False            CmbMark3.Enabled = False            CmbRelation2.Enabled = False            txtContent2.Enabled = False            txtContent3.Enabled = False        Else            CmbName2.Enabled = True            CmbMark2.Enabled = True            CmbRelation2.Enabled = True            txtContent2.Enabled = True        End If    End Sub    ' 第二个组合关系是否为空     Private Sub CmbRelation2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles CmbRelation2.SelectedIndexChanged        If CmbRelation2.Text = "" Then            CmbName3.Enabled = False            CmbMark3.Enabled = False            txtContent3.Enabled = False        Else            CmbName3.Enabled = True            CmbMark3.Enabled = True            txtContent3.Enabled = True        End If    End Sub

       2、建立子窗体

     如下图建立子窗体，然后选择要继承的父窗体，再然后神奇的事情便发生了：子窗体竟然和父窗体一模一样，一下子就省了不少时间~同样，在子窗体里重写类和方法就OK了，只需在U层这一层写就行。

      

      子窗体代码如下：

 Private Sub frmGroupStuInfo_Load(sender As Object, e As EventArgs) Handles MyBase.Load        '赋初值        CmbName1.Items.Add("卡号")        CmbName1.Items.Add("学号")        CmbName1.Items.Add("姓名")        CmbName1.Items.Add("性别")        CmbName1.Items.Add("专业")        CmbName1.Items.Add("年级")        CmbName1.Items.Add("班级")        CmbName2.Items.Add("卡号")        CmbName2.Items.Add("学号")        CmbName2.Items.Add("姓名")        CmbName2.Items.Add("性别")        CmbName2.Items.Add("专业")        CmbName2.Items.Add("年级")        CmbName2.Items.Add("班级")        CmbName3.Items.Add("卡号")        CmbName3.Items.Add("学号")        CmbName3.Items.Add("姓名")        CmbName3.Items.Add("性别")        CmbName3.Items.Add("专业")        CmbName3.Items.Add("年级")        CmbName3.Items.Add("班级")    End Sub    '把加载的汉字转换成数据库的字段     Public Overrides Function GetEnglish(cmbName As String) As String        Select Case cmbName            Case "卡号"                GetEnglish = "CardNo"            Case "学号"                GetEnglish = "StudentNo"            Case "姓名"                GetEnglish = "StudentName"            Case "性别"                GetEnglish = "Sex"            Case "专业"                GetEnglish = "Department"            Case "年级"                GetEnglish = "Grade"            Case "班级"                GetEnglish = "StudentClass"            Case "与"                GetEnglish = "and"            Case "或"                GetEnglish = "or"            Case Else                GetEnglish = ""        End Select    End Function    '传数据库表名     Protected Overrides Function GetdbName() As String        Return "Student_info"    End Function    '查询并把数据显示到datagridview中    Protected Overrides Sub Todgv(ByVal comQueryEntity As GroupInquireInfo)        Dim table As New DataTable        Dim frmGroupParent As New frmGroupParent        Dim GeneralFacade As New Facade.GeneralFacade        Try            table = GeneralFacade.FGroupCheck(comQueryEntity)            If table.Rows.Count = 0 Then                table.Clear()                dgv.DataSource = Nothing                dgv.Refresh()            Else                dgv.DataSource = table                dgv.Columns(0).Visible = False                dgv.Columns(0).HeaderText = "卡号"                dgv.Columns(1).HeaderText = "学号"                dgv.Columns(2).HeaderText = "姓名"                dgv.Columns(3).HeaderText = "专业"                dgv.Columns(4).HeaderText = "性别"                dgv.Columns(5).HeaderText = "年级"                dgv.Columns(6).HeaderText = "班级"                dgv.Columns(7).HeaderText = "金额"                dgv.Columns(8).HeaderText = "备注"                dgv.Columns(9).HeaderText = "是否结账"                dgv.Columns(10).HeaderText = "状态"                dgv.Columns(11).HeaderText = "用户类型"                dgv.Columns(12).HeaderText = "注册日期"                dgv.Columns(13).HeaderText = "注册时间"            End If        Catch ex As Exception            MsgBox(ex.Message, vbOKOnly, "提示")        End Try    End Sub

       3、DAL层数据库查询

 Public Function IGroupCheck(Groupcheck As Model.GroupInquireInfo) As DataTable Implements IGroupQuery.IGroupCheck        Dim sql As String        Dim table As DataTable        sql = "select * from " & Groupcheck.DbName & " where "        If Trim(Groupcheck.CmbRelation1) = "" Then  '有一组查询条件            sql = sql & Groupcheck.CmbName1 & Groupcheck.CmbMark1 & "'" & Groupcheck.TxtContent1 & "'"        Else            If Trim(Groupcheck.CmbRelation2) = "" Then '有两组查询条件                sql = sql & Groupcheck.CmbName1 & Groupcheck.CmbMark1 & "'" & Groupcheck.TxtContent1 & "'" & Groupcheck.CmbRelation1 & " " & Groupcheck.CmbName2 & Groupcheck.CmbMark2 & "'" & Groupcheck.TxtContent2 & "'"            Else                sql = sql & Groupcheck.CmbName1 & Groupcheck.CmbMark1 & "'" & Groupcheck.TxtContent1 & "'" & Groupcheck.CmbRelation1 & " " & Groupcheck.CmbName2 & Groupcheck.CmbMark2 & "'" & Groupcheck.TxtContent2 & "'" & Groupcheck.CmbRelation2 & " " & Groupcheck.CmbName3 & Groupcheck.CmbMark3 & "'" & Groupcheck.TxtContent3 & "'"            End If        End If        '模板的无参查询        table = sqlHelper.ExeSelectNo(sql, CommandType.Text)        Return table    End Function

       小结

       组合查询、一般查询都有好多类似功能的窗体，那么使用模板方法无疑会给我们带来很大的方便，它通过把不变行为搬移到超类，去除子类中的重复代码体现出了其优势。因此，对于设计模式，还是要韩信点兵——多多益善。