PropertyChanged event fires twice and should not

I have a class with two descendent classes (child, grandchild):

BaseSample
   |-ProcessData
       |-Measurement

When a property changes in the M开发者_运维问答easurement class I raise a OnCrucibleOxidizedMassChanged event:

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

For testing purposes, I have a module that tests this event-raising behavior. Note that ToteBinSample inherits from the BaseSample. In Main() I'm just testing what happens when you change the value of CrucibleOxidizedMass:

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

However, the OnChanged sub gets called twice, even though I only assign a value to CrucibleOxidizedMass once.

Do you have any idea why it gets fired twice and how I can correct it?

I found my mistake. I manually raised the PropertyChanged event within the OnCrucibleOxidizedMassChanged sub of the LINQ to SQL class, O2Measurement. So, I was causing the second firing of the PropertyChanged event. Thanks, msarchet, and any others who pondered this problem.

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