VB.NET & 策略模式（下机用户类型选择）

     上篇文章讲述了对于下机操作和基本数据设定的时间联系，今天主要就是应用“策略模式”来了解了解对于固定用户，以及临时用户之间的选择，看学习设计模式的时候自己对于策略模式的理解，我们可以把固定用户和临时用户封装起来，这样系统就可以按照用户的类型来进行选择了。当然前提首先要抽象一个类，来封装这两个用户类型。

看类图：

代码具体化：

首先看抽象类：BL_CashSuper,定义两种支持算法的公共接口

''' <summary>
''' 抽象类，定义所有支持算法的公共接口
''' </summary>
''' <remarks></remarks>
Public MustInherit Class BL_CashSuper
    '根据上机时间，卡的类型，计算出消费金额（抽象方法）
    Public MustOverride Function GetconsumeMondey(ByVal time As Integer) As Single
End Class

Imports Entity.RechargeEntity
Public Class BL_CashTmp : Inherits BL_CashSuper
    Dim QueryBasicdata As New BasicDataBLL   '实例化类BasicdataBLL
    Dim EnBasicdata As New Entity.BasicDataEntity    '定义基础数据实体
    Dim BasicdataList As IList(Of Entity.BasicDataEntity)   '定义实体的泛型集合
    Dim TmpHourCash As Single   '定义一个变量-存放临时用户每小时费用

    Public Overrides Function GetconsumeMondey(time As Integer) As Single
        '赋值给实体泛型集合
        BasicdataList = QueryBasicdata.ReadBasic(EnBasicdata)

        TmpHourCash = BasicdataList(0).TmpRate     '给变量赋值，临时用户每小时费用

        Dim Consumecash As Single    '定义变量存放消费金额
        Consumecash = CSng(time) * CSng(TmpHourCash / 60)    '计算消费金额（CSng把表达式转化成Single类型）
        Return Consumecash
    End Function

Imports Entity.RechargeEntity
''' <summary>
''' 具体策略类，计算会员用户消费金额，封装的具体的算法或行为，继承于类BL_CashSuper
''' </summary>
''' <remarks></remarks>
Public Class BL_CashVIP : Inherits BL_CashSuper
    Dim QueryBasicdata As New BasicDataBLL   '实例化类BasicdataBLL
    Dim EnBasicdata As New Entity.BasicDataEntity    '定义基础数据实体
    Dim BasicdataList As IList(Of Entity.BasicDataEntity)   '定义实体的泛型集合
    Dim VIPHourCash As Single   '定义一个变量-存放固定用户半小时费用

    Public Overrides Function GetconsumeMondey(time As Integer) As Single
        '赋值给实体泛型集合
        BasicdataList = QueryBasicdata.ReadBasic(EnBasicdata)

        VIPHourCash = BasicdataList(0).Rate    '给变量赋值，固定用户半小时费用

        Dim Consumecash As Single    '定义变量存放消费金额
        Consumecash = CSng(time) * CSng(VIPHourCash / 30)    '计算消费金额（CSng把表达式转化成Single类型）
        Return Consumecash
    End Function

Imports BLL
Imports System.Reflection
''' <summary>
''' 应用简单工厂，通过传入的卡的类型，来具体选择应用那个算法，加一个反射，这样才能完美的实现开发封闭的原则，当我再需要增加一个算法的时候，我只需要在另外增加一个B层就好，而无需修改任何地方
''' </summary>
''' <remarks></remarks>
Public Class BL_CashContext
    Private cashsuper As BL_CashSuper    '定义抽象类

    Public Sub New(ByVal CardType As String)

        '应用反射技术根据卡号类型自动选择应该实例化的类  ，优化简单工厂
        Dim strInstance As String = "BLL.BL_Cash" + CardType   'BL_Cash+(Tmp Or VIP)
        cashsuper = CType(Assembly.Load("BLL").CreateInstance(strInstance), BL_CashSuper)
    End Sub
    Public Function GetResult(ByVal time As Integer) As Single
        '调用相关的消费处理类计算收费方法
        Dim times As Single
        '具体计算
        times = cashsuper.GetconsumeMondey(time)
        Return times
    End Function

Select Case cardList(0).cardtype
            Case "固定用户"
                CardType = "VIP"
            Case "临时用户"
                CardType = "Tmp"
            Case Else
                CardType = ""
        End Select
        '实例化类BL_CashContext,传入用户类型
        Dim cashcontext As New BL_CashContext(CardType)
        '调用策略模式计算出余额并赋值给consumecash
        Dim consumecash As Single = cashcontext.GetResult(enline.consumeTime)
        '定义变量newbalance，用于存放最新的余额
        Dim newbalance As Single = CSng(QCardL(0).balance.ToString) - CSng(consumecash)

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