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。