实现INotifyPropertyChanged时出现问题

本文介绍了实现INotifyPropertyChanged时出现问题的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 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!