使用C＃從Windows Phone的列表框中刪除所選項目

Question

我想使用上下文菜單下拉框從列表框中刪除所選項目，這是我的XAML

  <ListBox Margin="3,60,1,10" Grid.Row="1" Name="lstNews" Tap="lstNews_Tap" Width="476" d:LayoutOverrides="VerticalMargin">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <StackPanel Grid.Row="1" Orientation="Horizontal" Height="120" Width="478">
                    <StackPanel.Background>
                        <ImageBrush ImageSource="Images/Text-ALU.png" Stretch="Fill" />
                    </StackPanel.Background>


                    <toolkit:ContextMenuService.ContextMenu>
                        <toolkit:ContextMenu>
                            <toolkit:MenuItem Header="Delete" Click="MenuItem_Click"/>
                            <toolkit:MenuItem Header="Open" Click="MenuItem_Click"/>

                        </toolkit:ContextMenu>
                    </toolkit:ContextMenuService.ContextMenu>


                    <Grid HorizontalAlignment="Left" Width="30" Background="#FF0195D5" Margin="0,0,0,2" Height="118">
                        <TextBlock x:Name="txtDate" TextWrapping="Wrap" Text="{Binding Path=newsDate}" RenderTransformOrigin="0.5,0.5" Margin="-43.169,44.001,-43.831,0" UseLayoutRounding="False" d:LayoutRounding="Auto" TextAlignment="Center" Height="30" VerticalAlignment="Top" Width="117">
                            <TextBlock.RenderTransform>
                                <CompositeTransform Rotation="-90"/>
                            </TextBlock.RenderTransform>
                        </TextBlock>
                    </Grid>
                    <Grid HorizontalAlignment="Left" Width="5" Height="120"/>
                    <StackPanel Orientation="Vertical" VerticalAlignment="Top" Width="432" Height="114">
                        <TextBlock x:Name="txtTitle" Height="27" TextWrapping="Wrap" Text="{Binding Path=newsTitle}" Foreground="Black" FontSize="18.667" HorizontalAlignment="Left" Width="432" FontWeight="Bold" />
                        <StackPanel Orientation="Horizontal" Width="432" Height="27">
                            <TextBlock x:Name="txtBy" Height="27" TextWrapping="Wrap" Text="{Binding Path=newsSource}" Foreground="Black" FontSize="18.667" Width="399"/>
                            <Image x:Name="imgArrow" Width="25" Source="Images/Go-In-Arrow.png" Height="25" Margin="5,0,0,0"/>
                        </StackPanel>
                        <StackPanel Orientation="Horizontal" Width="433" Height="60">
                            <TextBlock x:Name="txtDesc" Height="58" TextWrapping="Wrap" Foreground="Black" Text="{Binding Path=newsShortDescription}" FontSize="18.667" Width="371"/>
                            <TextBlock x:Name="txtID" Height="56" Text="{Binding Path=newsID}"  TextWrapping="Wrap" Foreground="Black" FontSize="18.667" Width="8" Visibility="Collapsed"/>
                            <Image x:Name="imgType" Width="35" Source="{Binding Path=newsTypeImage}" Height="40" Margin="27,20,0,0" d:LayoutOverrides="Height"/>
                        </StackPanel>
                    </StackPanel>
                </StackPanel>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>

這是我要對刪除事件“ MenuItem_Click”執行的操作，但是它會引發錯誤“只讀collection.supported不支持該操作。因此，刪除該單擊事件的所選項目的代碼是什么

 // this is code to delete i am trying-->  lstNews.Items.Remove(lstNews.SelectedItem.ToString());
      //below is code  im trying to set listboxitemsource
          private void FillListBox()
    {
        fulllist = new nList();
        lstNews.ItemsSource = fulllist;

    }

 public class nList : List<NewsData>
{
    StringData sd = new StringData();
    public IList<NewsData> GetLCList()
    {
        IList<NewsData> lcList = null;
        using (NewsDataContext context = new NewsDataContext(sd.news_string))
        {
            IQueryable<NewsData> query = (from app in context.NewsData select app).OrderByDescending(app => app.entryID);
            lcList = query.ToList();
        }
        return lcList;
    }

    public nList()
    {
        IList<NewsData> lcData = this.GetLCList();
        StringBuilder messageBuilder = new StringBuilder();
        foreach (NewsData lc in lcData)
        {

            Add(new NewsData
            {
                newsID = lc.newsID,
                newsTitle = lc.newsTitle,
                newsSource = lc.newsSource,
                newsDate = (new GetDate()).getdate(lc.newsDate),//(new AnnouncementList()).getdate(lc.newsDate),
                newsShortDescription = lc.newsShortDescription,
                newsTypeImage = lc.newsTypeImage,
                newsSharing = lc.newsSharing
            });
        }
    }
}

Answer 1

lstNews.Items是頁面上顯示的對象列表。 因此，此lstNews.Items是數據模板的集合，因此這就是為什么當您嘗試lstNews.Items.Remove(lstNews.SelectedItem.ToString())失敗了。

您應該使用lstNews.Items.Remove(lstNews.SelectedItem)刪除項目。

但從最佳實踐來看，最好從源而不是從列表中刪除項目。 即，您應該從fulllist刪除項目，然后將其重新分配為lstNews.ItemsSource = fulllist;

代碼中所做的更改

1. fulllist應該是ObservableCollection的一種，以便對數據所做的所有更改都可以反映到UI。 將List轉換為ObservableCollection可以使用以下代碼：

    fulllist = new ObservableCollection<NewsData>(new nList()); 

2. 添加用於從fulllist刪除數據的實現，可能的實現可能是：

    object obj = lstNews.SelectedItem; if(obj is NewsData){ fulllist.Remove((NewsData)obj); lstNews.ItemsSource = fulllist; }