VB.NET版机房收费系统之组合查询

第一次用VB做它的时候，用字符串拼接做了一个感觉特麻烦，当时在师傅的指导下了解到不用那么麻烦，将条件都设成一个个的变量，给他们一个默认值“1=1”，如果选择了一个条件，就给那个默认值覆盖掉就OK啦，所有这次果断就用他了。

界面：

U层：

    '定义一个实体
    Dim enCombination As New Entity.CombinationEntity

    Private Sub FrmStudentBasic_Load(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles MyBase.Load
        '给实体的值赋初值
        enCombination.ProField = "1"
        enCombination.ProFieldTwo = "1"
        enCombination.ProFieldThree = "1"
        enCombination.ProOperator = "="
        enCombination.ProOperatorTwo = "="
        enCombination.ProOperatorThree = "="
        enCombination.ProContent = "1"
        enCombination.ProContentTwo = "1"
        enCombination.ProContentThree = "1"
        enCombination.ProCombination = "and"
        enCombination.ProCombinationTwo = "and"
    End Sub

    '*********************************
    'U层查询上机状态的事件
    '返回值：dataTable
    '*******************************
    Private Sub btnInquire_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles btnInquire.Click

        '清空dataGridview控件的记录
        DataGridView1.DataSource = vbNull
        '判断输入是否有空值！
        If cmbField1.Text = "" Or cmbOperator1.Text = "" Or txtInquire1.Text = "" Then
            MsgBox("第一个查询条件有空！")
            Exit Sub
        Else
            If Not cmbCombination1.Text = "" Then
                If cmbField2.Text = "" Or cmbOperator2.Text = "" Or txtInquire2.Text = "" Then
                    MsgBox("第二个查询条件有空！")
                    Exit Sub
                Else
                    If Not cmbCombination2.Text = "" Then
                        If cmbField3.Text = "" Or cmbOperator3.Text = "" Or txtInquire3.Text = "" Then
                            MsgBox("第三个查询条件有空！")
                            Exit Sub
                        End If
                        '给实体赋值（第三个条件）
                        enCombination.ProCombinationTwo = GetEnglish(cmbCombination2.Text.ToString())
                        enCombination.ProFieldThree = GetEnglish(cmbField3.Text.ToString())
                        enCombination.ProOperatorThree = cmbOperator3.Text.ToString()
                        enCombination.ProContentThree = txtInquire3.Text.ToString()
                    End If
                End If
                '给实体赋值（第二个条件）
                enCombination.ProCombination = GetEnglish(cmbCombination1.Text.ToString())
                enCombination.ProFieldTwo = GetEnglish(cmbField2.Text.ToString())
                enCombination.ProOperatorTwo = cmbOperator2.Text.ToString()
                enCombination.ProContentTwo = txtInquire2.Text.ToString()
            End If
            '给实体赋值(第一个条件）
            enCombination.ProField = GetEnglish(cmbField1.Text.ToString())
            enCombination.ProOperator = cmbOperator1.Text.ToString()
            enCombination.ProContent = txtInquire1.Text.ToString()
        End If

        Dim studentBasic As New BLL.StudentBasicBLL
        Dim tb As New DataTable

        Try
            tb = studentBasic.InquireStudentBasic(enCombination)
        Catch ex As Exception
            MsgBox(ex.Message.ToString())
        End Try
        DataGridView1.DataSource = tb
    End Sub


    '****************************
    '函数：将控件中的汉字变为相应的英文
    '*********************************
    Public Function GetEnglish(ByVal strControl As String) As String
        Select Case (strControl)
            Case "卡号"
                Return "cardNo"
            Case "学号"
                Return "studentNo"
            Case "性别"
                Return "sex"
            Case "姓名"
                Return "studentName"
            Case "年级"
                Return "grade"
            Case "系别"
                Return "department"
            Case "班号"
                Return "class"
            Case "与"
                Return "and"
            Case "或"
                Return "or"
            Case Else
                Return ""

        End Select
    End Function

B层：

Public Function InquireStudentBasic(ByVal enCombination As Entity.CombinationEntity) As DataTable
        Dim dataAccess As New Factory.FactoryDataBase     '定义工厂
        Dim ICard As IDAL.ICard                           '定义接口
        Dim tb As New DataTable                           '定义一个DataTable

        ICard = dataAccess.CreateICard()                  '创建接口
        tb = ICard.SelectCard(enCombination)              '调用接口的方法
        Return tb                                         '返回值
    End Function

D层：

开始没有存储过程时：

'定义数据库连接对象，并利用反射将连接字符串赋给conn
        Dim conn As New SqlClient.SqlConnection
        conn.ConnectionString = ConfigurationManager.AppSettings("strConn")

        '定义执行sql查询语句
        Dim strSQL As String
        strSQL = "select * from View_StudentCard where " + enCombination.ProField + enCombination.ProOperator + " '" & enCombination.ProContent & "'" + " " + enCombination.ProCombination + " " + enCombination.ProFieldTwo + enCombination.ProOperatorTwo + "'" & enCombination.ProContentTwo & "' " + " " + enCombination.ProCombinationTwo + " " + enCombination.ProFieldThree + enCombination.ProOperatorThree + " '" & enCombination.ProContentThree & "'"
  '定义一个dataAdapter对象
        Dim da As New SqlDataAdapter(strSQL,conn)
        '定义一个dataTable对象
     Dim tb As New DataTable
        '将结果集填充到tb中()
        da.Fill(tb)
        '函数返回值
        Return tb

后来加上存储过程：

 Dim strSQL As String
        Dim paras As SqlParameter()

        enCombination.ProTableName = " View_StudentCard"     '确定数据库表名
        paras = New SqlParameter() {New SqlParameter("@cmbFieldA",enCombination.ProField),New SqlParameter("@cmbFieldB",enCombination.ProFieldTwo),New SqlParameter("@cmbFieldC",enCombination.ProFieldThree),New SqlParameter("@cmbOperatorA",enCombination.ProOperator),New SqlParameter("@cmbOperatorB",enCombination.ProOperatorTwo),New SqlParameter("@cmboperatorC",enCombination.ProOperatorThree),New SqlParameter("@txtInquireA",enCombination.ProContent),New SqlParameter("@txtInquireB",enCombination.ProContentTwo),New SqlParameter("@txtInquireC",enCombination.ProContentThree),New SqlParameter("@cmbCombinationA",enCombination.ProCombination),New SqlParameter("@cmbCombinationB",enCombination.ProCombinationTwo),New SqlParameter("@tableName",enCombination.ProTableName)
                                  }

        strSQL = "PROC_CombinationInquire"
        Dim tb As New DataTable
        tb = DAL.SqlHelper.ExecuteReader(strSQL,CommandType.StoredProcedure,paras)
        Return tb
    End Function

SQLHELPER里的ExecuteReader方法：

 '**********************************
    '带参数的返回结果集的sql查询或存储过程
    '参数：sql语句，command类型（存储过程为storedProcedure，其他为text），参数集合
    '返回值：datatable
    '**********************************
    Public Shared Function ExecuteReader(ByVal strSQL As String,ByVal cmdType As CommandType,ByVal paras As SqlParameter()) As DataTable
        Dim conn As New SqlClient.SqlConnection
        conn.ConnectionString = ConfigurationManager.AppSettings("strConn")

        Dim cmd As New SqlCommand(strSQL,conn)
        cmd.CommandType = cmdType
        cmd.Parameters.AddRange(paras)
        '打开数据库连接
        If conn.State = ConnectionState.Closed Then
            conn.Open()
        End If

        Dim reader As SqlDataReader
        Dim tb As New DataTable
        reader = cmd.ExecuteReader
        tb.Load(reader)

        '关闭数据库连接
        If conn.State = ConnectionState.Open Then
            conn.Close()

        End If

        Return tb
    End Function

创建存储过程：

create procedure PROC_StudentBasicInquire
@cmbFieldA varchar(20),@cmbOperatorn varchar(20),@txtInquireA varchar(20),@cmbCombinationA  varchar(20),@cmbFieldB  varchar(20),@cmbOperatorB  varchar(20),@txtInquireB  varchar(20),@cmbCombinationB  varchar(20),@cmbFieldC  varchar(20),@cmboperatorC varchar(20),@txtInquireC varchar(20),@TempSql varchar(20),@tableName  Sql varchar(20))         --tableName获取数据库表名的  
As
declare @TempSql varchar(500)--临时存放sql语句  
--CHAR(32)是空格,CHAR(39)单引号 
begin
set @TempSql='select * from ' +@tableName  +' where '+CHAR(32)+
@cmbFieldA +@cmbOperatorA+CHAR(39) +@txtInquireA +CHAR(39) +@cmbCombinationA +CHAR(32)+
 @cmbFieldB + @cmbOperatorB +CHAR(39)+ @txtInquireB  +CHAR(39) +@cmbCombinationB + CHAR(32)+
 @cmbFieldC + @cmboperatorC ++CHAR(39)+@txtInquireC+CHAR(39)
execute (@TempSql) 
end 

这样之后我们需要的那几个组合查询，就只需要创建一个存储过程，我们通过参数让他从不同的表里查询。

（编辑：李大同）

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