Question

我有一个有两个后代班级的班级（孩子，孙子）：

BaseSample
   |-ProcessData
       |-Measurement

当一个属性在Measurement类中发生变化时，我会引发一个OnCrucibleOxidizedMassChanged事件：

Protected Sub AddEventHandler(ByVal thisMeasurement As CalcinerDataAccess.O2Measurement)

    AddHandler thisMeasurement.PropertyChanged, AddressOf RaiseMassChanged

End Sub

Protected Sub RaiseMassChanged(ByVal sender As Object, ByVal e As EventArgs)

    Dim CrucibleOxidizedMassReadyToReport As Boolean = _
        (TypeOf e Is System.ComponentModel.PropertyChangedEventArgs) AndAlso _
        (CType(e, System.ComponentModel.PropertyChangedEventArgs).PropertyName = "CrucibleOxidizedMass" And _
            CType(sender, CalcinerDataAccess.O2Measurement).CrucibleOxidizedMass IsNot Nothing)

    If CrucibleOxidizedMassReadyToReport Then
        RaiseEvent OnCrucibleOxidizedMassChanged(sender, e)

    End If

End Sub

出于测试目的，我有一个测试此事件提升行为的模块。请注意，ToteBinSample继承自BaseSample。在Main（）中，我只是测试更改CrucibleOxidizedMass的值时会发生什么：

Sub Main()


    thisSample = New SampleTypeManager.SampleTypes.ToteBinSample
    AddHandler thisSample.OnCrucibleOxidizedMassChanged, AddressOf OnChanged

    thisSample.SampleData.ProcessDatas(0).O2Measurements(0).CrucibleOxidizedMass = 20

    Console.WriteLine("Done...")
    Console.Read()


End Sub

Private Sub OnChanged(ByVal sender As Object, ByVal e As EventArgs)

    Console.WriteLine("Time to send report!")

End Sub

然而，OnChanged子被调用两次，即使我只为CrucibleOxidizedMass赋值一次。

你知道为什么它被解雇了两次以及我如何纠正它？

Answer 1

我发现了自己的错误。我在LINQ to SQL类的O2Measurement的OnCrucibleOxidizedMassChanged子项中手动引发了PropertyChanged事件。所以，我导致了PropertyChanged事件的第二次触发。谢谢，msarchet和其他任何思考过这个问题的人。

Partial Class O2Measurement

    Private Sub OnCrucibleOxidizedMassChanged()
        'Here is my mistake -- I have removed it in my code
        RaiseEvent PropertyChanged(Me, New ComponentModel.PropertyChangedEventArgs("CrucibleOxidizedMass"))

    End Sub
End Class

PropertyChanged事件触发两次，不应该触发

1 个答案: