[.Net Concept]適時採用事件動態繫結來替代用If判斷作功能的啟用

July 18, 2010

Private _enableLogData As Boolean
Public Property EnableLogData() As Boolean
    Get
        Return _enableLogData
    End Get
    Set(ByVal value As Boolean)
        _enableLogData = value
    End Set
End Property

Event Executing As EventHandler
Event Executed As EventHandler

Protected Sub OnExecuting(ByVal e As EventArgs)
    RaiseEvent Executing(Me, e)
End Sub

Protected Sub OnExecuted(ByVal e As EventArgs)
    RaiseEvent Executed(Me, e)
End Sub

Sub GoExecute()
    For i As Integer = 1 To 100000000
        OnExecuting(New EventArgs)
        '運行動作，這邊為了看出差異，故不做動作
        If EnableLogData Then
                '紀錄動作，這邊為了看出差異，故不做動作
        End If
        OnExecuted(New EventArgs)
    Next
End Sub

End Class

    executor.EnableLogData = True
    sw.Reset()
    sw.Start()
    executor.GoExecute()
    Console.WriteLine(sw.ElapsedMilliseconds.ToString)
End Sub</pre></div>

Private _enableLogData As Boolean
Public Property EnableLogData() As Boolean
    Get
        Return _enableLogData
    End Get
    Set(ByVal value As Boolean)
        If _enableLogData &lt;&gt; value Then
            OnEnableLogDataChanging(New EventArgs)
            _enableLogData = value
            OnEnableLogDataChanged(New EventArgs)
        End If
    End Set
End Property

Event EnableLogDataChanging As EventHandler
Event EnableLogDataChanged As EventHandler
Event Executing As EventHandler
Event Executed As EventHandler

Protected Sub OnEnableLogDataChanging(ByVal e As EventArgs)
    RaiseEvent EnableLogDataChanging(Me, e)
End Sub

Protected Sub OnEnableLogDataChanged(ByVal e As EventArgs)
    RaiseEvent EnableLogDataChanged(Me, e)
End Sub

Protected Sub OnExecuting(ByVal e As EventArgs)
    RaiseEvent Executing(Me, e)
End Sub

Protected Sub OnExecuted(ByVal e As EventArgs)
    RaiseEvent Executed(Me, e)
End Sub

Sub GoExecute()
    For i As Integer = 1 To 100000000
        OnExecuting(New EventArgs)
        '運行動作，這邊為了看出差異，故不做動作
        OnExecuted(New EventArgs)
    Next
End Sub

Private Sub LogData(ByVal sender As Object, ByVal e As System.EventArgs)
    '紀錄動作，這邊為了看出差異，故不做動作        
End Sub

Private Sub Executor_EnableLogDataChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.EnableLogDataChanged
    RemoveHandler Executed, AddressOf LogData
    If EnableLogData Then
        AddHandler Executed, AddressOf LogData
    End If
End Sub

End Class

.NET Concept