机房收费系统--用户级别查询

     这几天做.NET版的机房收费系统的时候遇到了一个级别查询的问题关于DAL层我不怎么会写昨晚问了一下正权我终于会了，下面就贴出代码来

UI层：

'用来级别查询

Private SubcboOperatorLevel_SelectedIndexChanged(ByVal sender As System.Object, ByVal e AsSystem.EventArgs) Handles cboOperatorLevel.SelectedIndexChanged

        Dim EUser As New Entity.UserInfo'定义一个登录用户实体类

        Dim CheckUser As NewBLL.BLLAddOrDeleteUser '定义一个BLL层的BLLLogin类

        Dim dt As New DataTable '定义一个DataTable

        EUser.OperatorLevel =Trim(cboOperatorLevel.Text) '把级别传到EUser实体类里面

        dt = CheckUser.CheckUser(EUser)'调用AddUser的CheckUser函数

        gvwViewUserInfo.DataSource = dt'把DataTable的值传给Gvw控件

    End Sub

 

BLL层

 ‘级别查询

FunctionCheckUser(ByVal User As Entity.UserInfo) As DataTable

        Dim DalUser As NewDAL.DALUserInfo'定义一个DalUser为DALUserInfo类

        Dim EUser As NewEntity.UserInfo'定义一个实体类

        Dim dt As NewDataTable '定义一个DataTable

        EUser.OperatorLevel =User.OperatorLevel'把U层的OperatorLevel属性传给实体类EUser

        dt =DalUser.SelectLevel(EUser)’调用D层的SelectLevel方法

        Return dt

    End Function

 

最关键的是D层，D层由于用不同的方法就可以用同的SQL语句

D层

第一种普通的查询：

'连接数据库
    Dim con As String = " data source=.;initial catalog=Charge_System;user id =sa; password=123456"
   Dim conn As SqlConnection = New SqlConnection(con) 

Public Function SelectLevel(ByVal User As Entity.UserInfo) As System.Data.DataTable

Dim strSql As String = "select OperatorID as 用户名,OperatorNameas 用户姓名,OperatorLevel  as 用户级别 fromUser_Info where OperatorLevel =@OperatorLevel"‘SQL语句

        Dim cmd As SqlCommand = NewSqlCommand(strSql, conn)

        cmd.Parameters.Add(NewSqlParameter("@OperatorLevel", User.OperatorLevel))’把User.OperatorLevel的值传给@OperatorLevel

        Dim sqlda As New SqlDataAdapter‘定义一个SqlDataAdapter

        Dim ds As New DataSet’定义一个 DataSet

        Dim dt As New DataTable’定义一个DataTable

        Try

            conn.Open()‘打开数据库

           

‘把查到的内容填充到DataTabel中

sqlda.SelectCommand= cmd

            sqlda.Fill(dt)

            cmd.ExecuteReader()

 

            Return dt

        Catch ex As Exception

            Return dt

        End Try

 

    End Function

 

第二种，利用SQL视图

首先在数据库中建立一个视图，如图

然后D层代码为：

Dim strSql As String = "select * from V_User_Info where 用户级别=@OperatorLevel"‘SQL语句

        Dim cmd As SqlCommand = NewSqlCommand(strSql, conn)

        cmd.Parameters.Add(NewSqlParameter("@OperatorLevel", User.OperatorLevel))’把User.OperatorLevel的值传给@OperatorLevel

        Dim sqlda As New SqlDataAdapter‘定义一个SqlDataAdapter

        Dim ds As New DataSet’定义一个 DataSet

        Dim dt As New DataTable’定义一个DataTable

        Try

            conn.Open()‘打开数据库

           

‘把查到的内容填充到DataTabel中

sqlda.SelectCommand= cmd

            sqlda.Fill(dt)

            cmd.ExecuteReader()

 

            Return dt

        Catch ex As Exception

            Return dt

        End Try

 

    End Function

第三种利用存储过程（正在研究中）