策略模式--机房重构应用过

　　策略模式没有用在机房的下机结账，因为自己把临时用户给删了，为了使用策略模式就在充值功能上用到了。

　　UI层

    ''' <summary>
    ''' 确定充值
    ''' </summary>
    ''' <param name="sender"></param>
    ''' <param name="e"></param>
    Private Sub btnOk_Click(sender As Object, e As EventArgs) Handles btnOk.Click
        '判断控件是否为空
        If txtCardNo.Text = "" And txtPrint.Text = "" And txtRecharge.Text = "" Then
        Else
            Dim cc As CashContext
            cc = New CashContext(cmbCashContext.Text)
            result = cc.GetResult(Double.Parse(txtRecharge.Text))
            '卡号是否存在  是否退卡
            Dim CardInfo As New Entity.RechargeEntity
            CardInfo.CardNo = txtCardNo.Text.Trim
            CardInfo.State = "使用"
            Dim Facade As New Facade.SeekCardFacade
            Dim table As DataTable
            table = Facade.SeekCard(CardInfo)
            If table.Rows.Count = 0 Then
                MsgBox("没有此卡号或已经退卡！")
            Else
                '更改金额
                Dim RechargeCardInfo As New Entity.RechargeEntity
                RechargeCardInfo.CardNo = txtCardNo.Text.Trim
                RechargeCardInfo.RechCash = table.Rows(0).Item(1) + result
                RechargeCardInfo.State = "使用"
                Dim RechCashFacade As New Facade.RechargeFacade
                Dim strResult As Boolean
                strResult = RechCashFacade.RechargeCard(RechargeCardInfo)
                If strResult = False Then
                    MsgBox("没有此卡号！")
                Else
                    '添加充值记录
                    Dim RechargeInfo As New Entity.RechargeEntity
                    RechargeInfo.CardNo = txtCardNo.Text.Trim
                    RechargeInfo.RechCash = result

                    RechargeInfo.RechTime = FrmLogin.DayTime
                    RechargeInfo.Head = FrmLogin.AdminID
                    RechargeInfo.Computer = FrmLogin.Comptername 'FrmLogin .Computer
                    Dim RechargeFacade As New Facade.RechargeFacade
                    Dim Rresult As Boolean
                    Rresult = RechargeFacade.Recharge(RechargeInfo)
                    If Rresult = False Then
                        MsgBox("没有此卡号！")
                    Else
                        txtPrint.Text = "充值卡号为:" & RechargeInfo.CardNo & vbCrLf & vbCrLf & "充值金额是：" & RechargeInfo.RechCash + vbCrLf & vbCrLf & "充值时间为：" & Now & vbCrLf & vbCrLf & "充值老师为：" & RechargeInfo.Head
                        MsgBox("充值成功！")
                        txtCardNo.Text = ""
                        txtRecharge.Text = ""
                    End If
                End If
            End If
        End If
    End Sub
    Private Sub frmRecharge_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        'comboBox控件中添加选择内容
        Dim FieldRelation() As String      '定义存储变量
        FieldRelation = {"正常充值", "打折1.2", "冲200增50"} '存储变量中添加内容
        cmbCashContext.Items.AddRange(FieldRelation)  '添加内容
    End Sub

　　在Facade层写的策略模式

Public Class CashContext
    Public Cashsuper As CashSuper = Nothing
    Public Sub New(ByVal cardtype As String)
        Select Case cardtype
            Case "正常充值"
                Cashsuper = New CashNorMal()
            Case "打折1.2"
                Cashsuper = New CashRebate("1.2")
            Case "冲200增50"
                Cashsuper = New CashReturn("200", "50")
            Case ""
                Cashsuper = Nothing
        End Select
    End Sub
    Public Function GetResult(ByVal money As Double) As Double
        Return Cashsuper.acceptCash(money)
    End Function
End Class



''' <summary>
''' 抽象策略模式
''' </summary>
Public MustInherit Class CashSuper
    Public MustOverride Function acceptCash(ByVal money As Double) As Double

End Class
''' <summary>
''' 正常收费，继承CashSuper
''' </summary>
Public Class CashNorMal : Inherits CashSuper
    Public Overrides Function acceptCash(ByVal money As Double) As Double
        Return money
    End Function
End Class
''' <summary>
''' 打折收费，继承CashSuper
''' </summary>
Public Class CashRebate : Inherits CashSuper
    Public MoneyRebate As Double = 1D
    '通过构造函数传递参数
    Public Sub New（ByVal moneyRebate As String)
        Me.MoneyRebate = Double.Parse(moneyRebate)
    End Sub

    Public Overrides Function acceptCash(money As Double) As Double
        Return money * MoneyRebate
    End Function
End Class
''' <summary>
''' 返利收费，继承CashSuper
''' </summary>
Public Class CashReturn : Inherits CashSuper
    Private moneyCondition As Double = 0D
    Private moneyReturn As Double = 0D
    Public Sub New(ByVal moneyCondition As String, ByVal moneyReturn As String)
        Me.moneyCondition = Double.Parse(moneyCondition)
        Me.moneyReturn = Double.Parse(moneyReturn)
    End Sub

    Public Overrides Function acceptCash(money As Double) As Double
        Dim result As Double = money
        If money >= moneyCondition Then
            result = money - Math.Floor((money / moneyCondition)) * moneyReturn
        End If
        Return result
    End Function
End Class

　　这个策略模式就完成了，其他层的代码该咋写咋写，就是在充值金额上做了变动，其他的还是按照原来的7层写就好了。
　　在UI层中凡是涉及到逻辑判断的都应该放到BLL层判断的，但是当时自己知道的比较少，改和重写没有区别就不改了，这里也是可以用职责链的。
　　我们在机房重构中无意中用到了很多的设计模式，7层中的Facade层实际上就是外观模式的应用，但是我们没有意识到;还有Factory层，也是一个设计模式的应用,反射+配置文件实现数据的访问。（是不是抽象工厂就不了解了）。