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为什么ListBox AlternationIndex总是返回0

更新时间:2023-02-19 22:19:32

对于ListBoxListView,您将必须在ListBoxItem/ListViewItem上找到属性,如下所示:

     <TextBlock Text="{Binding Path=(ItemsControl.AlternationIndex), 
                       RelativeSource={RelativeSource AncestorType=ListBoxItem}, Converter={StaticResource IncCnvrtr}}" 
                       Foreground="DimGray" FontSize="20" FontWeight="Bold"  
                        HorizontalAlignment="Left" Margin="5,5,15,5" />

差异是由于ItemsControl仅生成一个ContentPresenter而成为一个项目的容器,而相同的ContentPresenter也正在加载DataTemplate.

但是对于ListBoxListBoxItem是项目容器,并且DataTemplate将由ListBoxItemTemplate中的ContentPresenter加载.因此,ListBoxItemItemsControl.AlternationIndex属性的值将根据索引而变化,但是加载DataTemplateContentPresenterItemsControl.AlternationIndex属性的值将始终为0,这是默认值. /p>

Ok, I know there are a couple of other similar questions to this but I am having a real issue with getting the AlternationIndex to work on ListBox or ListView.

my xaml is such:

            <ListBox BorderThickness="0" Name="RecentItemsListBox" HorizontalAlignment="Stretch"
                     ScrollViewer.HorizontalScrollBarVisibility="Disabled" 
                     ItemsSource="{Binding Path=RecentFilesList}" AlternationCount="100">
                <ListBox.ItemsPanel>

                    <ItemsPanelTemplate>
                        <WrapPanel />
                    </ItemsPanelTemplate>
                </ListBox.ItemsPanel>

                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <TextBlock Text="{Binding Path=(ItemsControl.AlternationIndex), 
                                    RelativeSource={RelativeSource Mode=TemplatedParent}, Converter={StaticResource IncCnvrtr}}" 
                                       Foreground="DimGray" FontSize="20" FontWeight="Bold"  
                                       HorizontalAlignment="Left" Margin="5,5,15,5" />
                            <StackPanel VerticalAlignment="Center">
                                <TextBlock Text="{Binding ClassName}" Foreground="Black" />
                                <TextBlock Text="{Binding DisplayName}" Foreground="Black" />
                            </StackPanel>
                        </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>

the converter increments the value by 1. This works fine and I have debugged it to confirm the value being sent to the converter is ALWAYS 0.

The crazy thing is this is only for ListBox or ListView

as soon as I change it to an ItemsControl the indexing is correct but I don't want an items control, I want a list box with all the features that come with it.

If you have any idea as to why this might be happening I'd be grateful for your help.

Thanks

Kieran

For ListBox or ListView you will have to find the property on the ListBoxItem/ListViewItem as below:

     <TextBlock Text="{Binding Path=(ItemsControl.AlternationIndex), 
                       RelativeSource={RelativeSource AncestorType=ListBoxItem}, Converter={StaticResource IncCnvrtr}}" 
                       Foreground="DimGray" FontSize="20" FontWeight="Bold"  
                        HorizontalAlignment="Left" Margin="5,5,15,5" />

The difference is due the fact that ItemsControl only generates a single ContentPresenter which becomes the Container of an item, and the same ContentPresenter is also loading the DataTemplate.

But for ListBox, ListBoxItem are the item containers and DataTemplate will be loaded by the ContentPresenter in Template of ListBoxItem. So value of ListBoxItem's ItemsControl.AlternationIndex property will change according to the index but the value of the ItemsControl.AlternationIndex property of the ContentPresenter that loads the DataTemplate will always be 0, which is the default value.