导读:在机房重构中,有好些个查询都是大同小异,最为显著的就是组合查询了。怎样给自己省事儿,相同的东西能不能重复利用,就成了一个现实的问题。第一遍做机房的时候,使用的更多的是:复制+粘贴。学习了设计模式后,可以用模板方法解决。这篇文章,就通过窗体继承和模板方法,实现组合查询。
观点:组合查询在机房中有3中情况,其实,组合查询完全可以看到是一种查询情况。
一、窗体继承的使用
1,首先建立一个父窗体
2,添加一个新项
3,选择继承窗体
4,确定后,一个新的继承窗体就好了。
二、模板方法的使用
备注:定义一个组合查询的实体,方便传参
1,首先在U层写入基础方法和传参
<span style="font-size:18px;">Public Class FrmGroupQueryPublic enGroupQuery As New Model.GroupQueryM '定义一个实体参数Private Sub Button1_Click_1(sender As Object, e As EventArgs) Handles btnQuery.Click'第一行组合关系为空If cmbRelation1.Text = "" Then'判断第一行控件内容是否为空If cmbField1.Text = "" ThenMsgBox("请输入字段名")ElseIf cmbOperation1.Text = "" ThenMsgBox("请输入操作符")ElseIf txtContent1.Text = "" ThenMsgBox("请输入要查询的内容")End IfEnd If' 当第一个组合关系不为空时 If cmbRelation1.Text <> "" ThenIf cmbField1.Text = "" ThenMsgBox("请输入字段名")ElseIf cmbOperation1.Text = "" ThenMsgBox("请输入操作符")ElseIf txtContent1.Text = "" ThenMsgBox("请输入要查询的内容")ElseIf cmbField2.Text = "" ThenMsgBox("请输入字段名")ElseIf cmbOperation2.Text = "" ThenMsgBox("请输入操作符")ElseIf txtContent2.Text = "" ThenMsgBox("请输入要查询的内容")End IfEnd If' 当第二个组合关系不为空时 If cmbRelation2.Text <> "" ThenIf cmbField1.Text = "" ThenMsgBox("请输入字段名")ElseIf cmbOperation1.Text = "" ThenMsgBox("请输入操作符")ElseIf txtContent1.Text = "" ThenMsgBox("请输入要查询的内容")ElseIf cmbField2.Text = "" ThenMsgBox("请输入字段名")ElseIf cmbOperation2.Text = "" ThenMsgBox("请输入操作符")ElseIf txtContent2.Text = "" ThenMsgBox("请输入要查询的内容")ElseIf cmbField3.Text = "" ThenMsgBox("请输入字段名")ElseIf cmbOperation3.Text = "" ThenMsgBox("请输入操作符")ElseIf txtContent3.Text = "" ThenMsgBox("请输入要查询的内容")End IfEnd If'给实体层传参Dim enGroupQuery As New Model.GroupQueryMenGroupQuery._field1 = GetDBName(cmbField1.Text.Trim())enGroupQuery._field2 = GetDBName(cmbField2.Text.Trim())enGroupQuery._field3 = GetDBName(cmbField3.Text.Trim())enGroupQuery._operate1 = cmbOperation1.Text.Trim()enGroupQuery._operate2 = cmbOperation2.Text.Trim()enGroupQuery._operate3 = cmbOperation3.Text.Trim()enGroupQuery._content1 = txtContent1.Text.Trim()enGroupQuery._content2 = txtContent2.Text.Trim()enGroupQuery._content3 = txtContent3.Text.Trim()enGroupQuery._relation1 = GetDBName(cmbRelation1.Text.Trim())enGroupQuery._relation2 = GetDBName(cmbRelation2.Text.Trim())enGroupQuery.GetTable = GetTable() '通过函数的返回值给参数赋值'给B层GroupQuery方法传递参数Dim FGroupQuery As New Facade.GroupQuertFADim table As DataTabletable = FGroupQuery.GroupQuery(enGroupQuery)If table.Rows.Count = 0 ThenMsgBox("没有记录,请重新设置查询条件", vbOKOnly, vbExclamation)DataGridView1.DataSource = NothingElseDataGridView1.DataSource = FGroupQuery.GroupQuery(enGroupQuery)End IfEnd Sub' 定义虚函数GetDBName,获取不同数据库的字段名 Protected Overridable Function GetDBName(ByVal control As String) As StringReturn ""End Function' 定义虚函数GetDBName,获取不同数据库的表名 Protected Overridable Function GetTable() As StringReturn ""End FunctionPrivate Sub Button2_Click_1(sender As Object, e As EventArgs) Handles btnExit.ClickMe.Close()End Sub'组合关系一不为空后,显示第二行查询条件Private Sub cmbRelation1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cmbRelation1.SelectedIndexChangedcmbField2.Enabled = TruecmbOperation2.Enabled = TruecmbRelation2.Enabled = TruetxtContent2.Enabled = TrueEnd Sub'组合关系二不为空后,显示第三行查询条件Private Sub cmbRelation2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cmbRelation2.SelectedIndexChangedcmbField3.Enabled = TruecmbOperation3.Enabled = TruetxtContent3.Enabled = TrueEnd SubEnd Class</span>
2,在B层,对D层数据库的查询结果做出处理
<span style="font-size:18px;">Imports Charge.IDAL
Imports Charge.Model
Public Class GroupQueryBLL''' <summary>''' 根据组合查询D层的返回结果,判断是否有值''' </summary>''' <param name="enGroupQuery"></param>''' <returns>没有值,不返回任何东西,有,就返回信息</returns>''' <remarks></remarks>Public Function GroupQueryStudent(ByVal enGroupQuery As Model.GroupQueryM) As DataTableDim factory As New Factory.CreateFactoryDim IGroupQuery As IGroupQuery = factory.CreateGroupQueryDim table As DataTable = IGroupQuery.GroupQuery(enGroupQuery)'检查D层返回的数据表中是否有数据If table.Rows.Count = 0 ThenReturn NothingElseReturn tableEnd IfEnd Function
End Class</span>
3,在D层对数据进行查询
<span style="font-size:18px;">/**********************************************
'类名:SQLGroupQuery
'命名空间:ChargeDAL
'创建时间:2015/1/5 20:58:39
'创建人:HXX
'修改时间:
'修改人:
'版本号:4.0.30319.18449
'说明:实现组合条件的
'版权:HHX
'/**********************************************
Imports System.Data.SqlClient
Imports System.Data
Imports ChargePublic Class SQLGroupQuery : Implements IDAL.IGroupQuery''' <summary>''' 根据设置的条件,进行信息查询''' </summary>''' <param name="enGroupQuery"></param>''' <returns>返回查询结果信息的集合</returns>Public Function GroupQuery(enGroupQuery As Model.GroupQueryM) As DataTable Implements IDAL.IGroupQuery.GroupQueryDim strSQL As String = "QueryGroup" '调用存储过程 Dim prams As SqlParameter() = {New SqlParameter("@cmbField1", enGroupQuery._field1),New SqlParameter("@cmbField2", enGroupQuery._field2),New SqlParameter("@cmbField3", enGroupQuery._field3),New SqlParameter("@cmbOperation1", enGroupQuery._operate1),New SqlParameter("@cmbOperation2", enGroupQuery._operate2),New SqlParameter("@cmbOperation3", enGroupQuery._operate3),New SqlParameter("@txtContent1", enGroupQuery._content1),New SqlParameter("@txtContent2", enGroupQuery._content2),New SqlParameter("@txtContent3", enGroupQuery._content3),New SqlParameter("@cmbRelation1", enGroupQuery._relation1),New SqlParameter("@cmbRelation2", enGroupQuery._relation2),New SqlParameter("@tableName", enGroupQuery.GetTable)} '设置参数Dim MyHelper As New SqlHelperDim table As New DataTabletable = MyHelper.ExecSelect(strSQL, CommandType.StoredProcedure, prams)Return tableEnd Function
End Class</span>
三、在继承窗体中的应用
在继承窗体中,需要重写模板父窗体中的方法,关键点有:字段的转换,数据表的返回。
<span style="font-size:18px;"> Private Sub FrmOperateWorkLog_Activated(sender As Object, e As EventArgs) Handles Me.Activated'避免一个窗体多次打开,或者打开多个操作窗体Dim frm As Form'遍历打开了的每一个窗体For Each frm In Application.OpenForms'如果当前窗体不是主窗体或者没有被打开过If frm.Name <> Me.Name And frm.Name <> FrmMain.Name And frm.Name <> FrmLine.Name Then'其他打开的窗体最小化frm.WindowState = 1End IfNextEnd SubPrivate Sub FrmMaintainInfo_Load(sender As Object, e As EventArgs) Handles MyBase.Load'给字段赋值cmbField1.Items.AddRange({"教师", "注册日期", "注册时间", "注销日期", "注销时间", "机器名"})cmbField2.Items.AddRange({"教师", "注册日期", "注册时间", "注销日期", "注销时间", "机器名"})cmbField3.Items.AddRange({"教师", "注册日期", "注册时间", "注销日期", "注销时间", "机器名"})cmbOperation1.Items.AddRange({"=", "<", ">", "<>"})cmbOperation2.Items.AddRange({"=", "<", ">", "<>"})cmbOperation3.Items.AddRange({"=", "<", ">", "<>"})cmbRelation1.Items.AddRange({"与", "或"})cmbRelation2.Items.AddRange({"与", "或"})End Sub'重写获得表名方法Protected Overrides Function GetTable() As StringenGroupQuery.GetTable = "TC_WorkLogInfo"Return enGroupQuery.GetTable()End Function'重写转换成数据库字段方法Protected Overrides Function GetDBName(control As String) As StringSelect Case (control)Case "教师"Return "UserID"Case "注册时间"Return "OnTime"Case "注册日期"Return "OnDate"Case "注销时间"Return "OffTime"Case "注销日期"Return "OffDate"Case "机器名"Return "Computer"Case "或"Return "or"Case "与"Return "and"Case ElseReturn ""End SelectEnd Function
End Class
</span>
到这里,利用窗体继承和模板方法进行组合查询就算是实现了。
四、应用说明
1,这里的返回类型都是DataTable,如果将其换为List,则就没有这么简单了。还需要多写一步(存储过程中),就像返回查询表格的参数一样,将查询表格的参数写到List中的表。
2,这里D层的查询是通过调用的存储过程,对存储过程的使用和理解,将在下一篇博客中详细说明。不过,在这里可以替换成一种类型,就像是第一次做机房时那样。例(第一次机房中):
<span style="font-size:18px;">txtSQL = txtSQL & tiaojian(Trim(cobozd1(0).Text)) & Trim(cobocz1(0).Text) & "'" & Trim(txtnr1.Text) & "'" _& " and " _& tiaojian(Trim(cobozd1(1).Text)) & Trim(cobocz1(1).Text) & " '" & Trim(txtnr2.Text) & "'" _& " and " _& tiaojian(Trim(cobozd1(2).Text)) & Trim(cobocz1(2).Text) & " '" & Trim(txtnr3.Text) & "'"</span>
在这里,也可以将存储过程,换成一般的文本类型查询。因为是应用的参数赋值,使用字符拼接的方式,将组合查询的三个情况看做是一种情况,也是可行的。五、个人感想
学以致用,学了还要会用才行。刚开始学了设计模式的时候,真的感受不大。但用上了之后,真的觉得很方便。只是在用的过程中有点艰难,不过,把一个个的问题解决了,最后实现了,感觉真的很良好。