组合查询一直是我一个头疼的事情，经过我不懈努力，终于在看了多次博客找了n多资料后实现了，现在拿出来和大家共享，希望大家指正！

首先是界面：

然后我们分层来看，B层实现对汉字向英文字符的转换：

'/************************************************* 
'作者：许恕
'小组：  
'说明:转换组合查询汉字为代码的类
'创建日期：2013.3.8
'版本号：v1.0.0
'*********************************************/

Public Class CombineCheckChangeStringBLL

    '     /// <summary>
    '     /// depiction：<改方法是转换上下机字符>
    '        /// </summary>
    '        /// <param name="<strCombineString>"><上下机实体></param>
    '             /// <returns>
    '             ///<返回上下机实体>
    '     /// </returns>
    Public Function ChangeOnlineRecordString(strCombineString As Entity.CombineSelectEntity) As Entity.CombineSelectEntity
        '转换字段
        strCombineString.FieldName1 = ChangeOnlineRecordFieldName(strCombineString.FieldName1)
        strCombineString.FieldName2 = ChangeOnlineRecordFieldName(strCombineString.FieldName2)
        strCombineString.FieldName3 = ChangeOnlineRecordFieldName(strCombineString.FieldName3)
        '装换操作符
        strCombineString.OperationalChar1 = ChangeOperationalChar(strCombineString.OperationalChar1)
        strCombineString.OperationalChar2 = ChangeOperationalChar(strCombineString.OperationalChar2)
        strCombineString.OperationalChar3 = ChangeOperationalChar(strCombineString.OperationalChar3)
        '转换关系符
        strCombineString.Relationchar1 = ChangeRelationchar(strCombineString.Relationchar1)
        strCombineString.Relationchar2 = ChangeRelationchar(strCombineString.Relationchar2)
        Return strCombineString

    End Function

'      /// <summary>
    '     /// depiction：<改方法是转换上下机字符-字段>
    '        /// </summary>
    '        /// <param name="<strOnline>"><上下机字符></param>
    '             /// <returns>
    '             ///<返回上字符串>
    '     /// </returns>
    Public Function ChangeOnlineRecordFieldName(strOnline As String) As String
        Dim strOnlineReturn As String
        Select Case strOnline
            Case "卡号"
                strOnlineReturn = "card_id"
            Case "上机日期"
                strOnlineReturn = "online_date"
            Case "上机时间"
                strOnlineReturn = "online_time"
            Case "机房号"
                strOnlineReturn = "computer_no"
            Case Else
                strOnlineReturn = ""
        End Select
        Return strOnlineReturn
    End Function
 '      /// <summary>
    '     /// depiction：<改方法是转换字符-操作符>
    '        /// </summary>
    '        /// <param name="<strOnline>"><上下机字符></param>
    '             /// <returns>
    '             ///<返回上字符串>
    '     /// </returns>
    Public Function ChangeOperationalChar(strChange As String) As String
        Dim strRenturn As String
        Select Case strChange
            Case "大于"
                strRenturn = " > "
            Case "小于"
                strRenturn = " < "
            Case "等于"
                strRenturn = " = "
            Case "不等于"
                strRenturn = " <> "
            Case Else
                strRenturn = " "
        End Select
        Return strRenturn
    End Function

    '      /// <summary>
    '     /// depiction：<改方法是转换关系字符>
    '        /// </summary>
    '        /// <param name="<strOnline>"><上下机字符></param>
    '             /// <returns>
    '             ///<返回上字符串>
    '     /// </returns>
    Public Function ChangeRelationchar(strChange As String) As String
        Dim strRenturn As String
        Select Case strChange
            Case "并且"
                strRenturn = "  and  "
            Case "或者"
                strRenturn = "  or   "
            Case Else
                strRenturn = ""
        End Select
        Return strRenturn
    End Function
End Class
'/************************************************* 
'作者：许恕
'小组：  
'说明:上机事务的类
'创建日期：2013.2.28
'版本号：v1.0.0
'*********************************************/
Public Class OnlineBLL
'     /// <summary>
    '     /// depiction：<改方法是组合查询上机信息>
    '        /// </summary>
    '        /// <param name="<checkString>"><组合查询实体></param>
    '             /// <returns>
    '             ///<返回datatable>
    '     /// </returns>
    Public Function CombineCheckOnlineRecord(enCheckString As Entity.CombineSelectEntity) As DataTable
        '改变组合查询的字符为英文
        Dim ChangeStringBLL As New CombineCheckChangeStringBLL
        enCheckString = ChangeStringBLL.ChangeOnlineRecordString(enCheckString)


        '查询内容
        Dim RecordFactory As New Factory.RecordFactory
        Dim IOnlineRecordDAL As IDAL.IOnLineRecordSeverDAL
        Dim OnlineDataTable As DataTable
        IOnlineRecordDAL = RecordFactory.CreatOnLineRecordSeverDAL()
        OnlineDataTable = IOnlineRecordDAL.CombineCheckOnlineRecord(enCheckString)


        '返回查询到的内容
        Return OnlineDataTable


    End Function


End Class

放到DAL 层我们的实现就简单了，我们拼接字符串查询就可以了

Imports System
Imports System.Data
Imports System.Data.sqlClient
Imports System.Configuration

'/************************************************* 
'作者：许恕
'小组：  
'说明:组合查询字符组合成sql的类
'创建日期：2013.3.9
'版本号：v1.0.0
'*********************************************/

Public Class GroupCombinesqlStringDAL

    '     /// <summary>
    '     /// depiction：<改方法是组合上机查询语句>
    '        /// </summary>
    '        /// <param name="<enCheckString>"><组合查询字符实体></param>
    '             /// <returns>
    '             ///<返回string>
    '     /// </returns>
    Public Shared Function GroupOnlinesqlString(enCheckString As Entity.CombineSelectEntity) As String
        Dim strsql As String
        strsql = "Select * from T_OnLineRecord where " & enCheckString.FieldName1 & enCheckString.OperationalChar1 & " @SelectString1  "

        If enCheckString.Relationchar1 = "" Then
            Return strsql
        End If

        strsql = strsql & enCheckString.Relationchar1 & " " & enCheckString.FieldName2 & enCheckString.OperationalChar2 & " @SelectString2  "

        If enCheckString.Relationchar2 = "" Then
            Return strsql
        End If

        strsql = strsql & enCheckString.Relationchar1 & " " & enCheckString.FieldName2 & enCheckString.OperationalChar2 & " @SelectString2  "

        Return strsql

    End Function
End Class

'/************************************************* 
'作者：许恕
'小组：  
'说明:对用户表操作的类
'创建日期：2013.2.28 16:00
'版本号：v1.0.0
'*********************************************/
Public Class sqlSeverOnLineRecordSeverDAL : Implements IDAL.IOnLineRecordSeverDAL
'     /// <summary>
    '     /// depiction：<改方法是组合查询记录>
    '        /// </summary>
    '        /// <param name="<enCard>"><查询实体></param>
    '             /// <returns>
    '             ///<返回datatable>
    '     /// </returns>
Public Function CombineCheckOnlineRecord(enCheckString As Entity.CombineSelectEntity) As DataTable Implements IDAL.IOnLineRecordSeverDAL.CombineCheckOnlineRecord
        '创建sqlhelper类
        Dim usersqlHelper As New sqlHelper.sqlHelper

        'sql语句
        Dim strsql As String
        Dim OnlineDataTable As DataTable


        'SQL查询语句  
        strsql = GroupCombinesqlStringDAL.GroupOnlinesqlString(enCheckString)

        '设置参数  
        
        Dim sqlParams As sqlParameter()
        If enCheckString.Relationchar1 = "" Then
            sqlParams = {
            New sqlParameter("@SelectString1",enCheckString.SelectString1)
            }
        End If

        If enCheckString.Relationchar2 = "" And enCheckString.Relationchar1 <> "" Then
            sqlParams = {
            New sqlParameter("@SelectString1",enCheckString.SelectString1),New sqlParameter("@SelectString2",enCheckString.SelectString2)
            }
        End If

        If enCheckString.Relationchar2 <> "" And enCheckString.Relationchar1 <> "" Then
            sqlParams = {
            New sqlParameter("@SelectString1",enCheckString.SelectString2),New sqlParameter("@SelectString3",enCheckString.SelectString3)
            }
        End If

        
        '执行  
        OnlineDataTable = usersqlHelper.ExecuteSelect(strsql,CommandType.Text,sqlParams)

        Return OnlineDataTable
    End Function
End Class

最后是结果：我们艰苦的奋斗有了结果：

原文链接：https://www.f2er.com/vb/259141.html

vb.net机房收费系统—组合查询的实现

首先是界面：

然后我们分层来看，B层实现对汉字向英文字符的转换：

放到DAL 层我们的实现就简单了，我们拼接字符串查询就可以了

最后是结果：我们艰苦的奋斗有了结果：

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