Problem implementing INotifyPropertyChanged

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Hi everyone!

I have been looking at my code for so long that I cannot longer see what is wrong with it.

I have a class Survey that implements INotifyPropertyChanged. There are two properties relevant to my question, TotalPoints and TotalAdjustedPoints:

VB

Public Property TotalPoints() As Long
      Get
          TotalPoints = lTotalPoints
      End Get
      Set(ByVal value As Long)
          If value <> lTotalPoints Then
              Me.lTotalPoints = value
              NotifyPropertyChanged("TotalPoints")
          End If
      End Set
  End Property

  Public Property TotalAdjustedPoints() As Long
      Get
          TotalAdjustedPoints = lTotalAdjustedPoints
      End Get
      Set(ByVal value As Long)
          If value <> lTotalAdjustedPoints Then
              Me.lTotalAdjustedPoints = value
              NotifyPropertyChanged("TotalAdjustedPoints")
          End If
      End Set
  End Property

I have an ObservableCollection of Survey instances that is used as ItemsSource for a list view. The listview is defined in XAML, like this:

XML

<ListView Name="lvSurveyManagement" Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="4" Margin="5,5,5,5">
    <ListView.View>
        <GridView>
            <GridViewColumn  x:Name="colSurveyGUID"  Width="300" DisplayMemberBinding="{Binding Path=SurveyGUID}"/>
            <GridViewColumn  x:Name="colSurveyLineGUID"  Width="100" DisplayMemberBinding="{Binding Path=LineGUID}"/>
            <GridViewColumn  x:Name="colSurveyType"  Width="100" DisplayMemberBinding="{Binding Path=SurveyType}"/>
            <GridViewColumn  x:Name="colLoadedPoints"  Width="122" DisplayMemberBinding="{Binding Path=TotalPoints}"/>
            <GridViewColumn  x:Name="colAdjustedPoints"  Width="122" DisplayMemberBinding="{Binding Path=TotalAdjustedPoints}"/>
        </GridView>
    </ListView.View>
</ListView>

When I update the above mentioned properties for a Survey object belonging to the ObservableCOllection, the change in TotalAdjustedPoints is reflected in the listview, but the change in TotalPoints is not.

I honestly don't see what I am doing wrong, hope someone here can help me. Thank you in advance.

Posted 8-Nov-11 6:42am

iris.frigole

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iris.frigole · Answer 1 · 2011-11-09T05:44:00

Ok... nothing like asking the question to see what was wrong with my code!

It turns out I was updating the properties like this:

VB

bDelete = Me.pSurvey.deleteSurveyPoints()
            If bDelete Then
                '...
                Me.pSurvey.TotalPoints = 0 'DOES NOT WORK
                Me.pSurvey.TotalAdjustedPoints = 0 'WORKS OK

But the problem was that inside Survey.deleteSurveyPoints I had a line:

Me.lTotalPoints = 0

Hence value <> lTotalPoints (property set) would never be verified and the PropertyChanged event would never be raised!