实现INotifyPropertyChanged时出现问题 [英] Problem implementing INotifyPropertyChanged

问题描述

大家好！

我已经看了很长时间的代码，以至于再也看不到它出了什么问题.

我有一个实现INotifyPropertyChanged的Survey类.与我的问题相关的两个属性是TotalPoints和TotalAdjustedPoints:

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:

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

我有一个ObservableCollection of Survey实例，用作列表视图的ItemsSource.列表视图是在XAML中定义的，如下所示:

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

<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>

当我更新属于ObservableCOllection的Survey对象的上述属性时，TotalAdjustedPoints的更改会反映在列表视图中，而TotalPoints的更改则不会.

老实说，我看不到我在做什么，希望这里有人可以帮助我.预先谢谢您.

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.

推荐答案

好吧...没什么比问问题来查看我的代码有什么问题了！

原来我正在更新这样的属性:

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

It turns out I was updating the properties like this:

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

但是问题是在Survey.deleteSurveyPoints内部，我有一行:

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

Me.lTotalPoints = 0

因此，值<> lTotalPoints(属性集)将永远不会被验证，PropertyChanged事件将永远不会被引发！

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

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