使用C#从Windows Phone的列表框中删除所选项目 [英] Delete selected item from listbox in windowsphone using c#
问题描述
我要使用上下文菜单下拉框从列表框中删除所选项目，这是我的xaml
i want delete selected item from my listbox using context menu drop-down box here is my 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>
这是我要对删除事件"MenuItem_Click"执行的操作，但会引发错误只读集合不支持该操作.因此，删除该单击事件的所选项目的代码是什么
here is what i am trying to do on delete event "MenuItem_Click" but than it throws error "Operation not supported on read-only collection.so what is code to delete selected item on that click event
// 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
});
}
}
}
推荐答案
lstNews.Items是页面上显示的对象列表.因此，此lstNews.Items是您的数据模板的集合，因此这就是为什么当您尝试lstNews.Items.Remove(lstNews.SelectedItem.ToString())时失败了.
lstNews.Items is list of object that are displayed on the page. So this lstNews.Items is collection of your datatemplate so that is why when you tried lstNews.Items.Remove(lstNews.SelectedItem.ToString()) than this fails.
您应该使用lstNews.Items.Remove(lstNews.SelectedItem)删除项目.
you should use lstNews.Items.Remove(lstNews.SelectedItem) to delete item.
但是为了最佳实践，最好从源中而不是从列表中删除项目.即您应该从fulllist中删除项目，然后将其重新分配为lstNews.ItemsSource = fulllist;
But for best practice it is prefered to delete item from the source not from the list. i.e. You should delete item from fulllist and reassign it as lstNews.ItemsSource = fulllist;
您的代码中所做的更改
fulllistshould be a type of ObservableCollection so that all the changes done on data can be reflected to UI. To convert List to ObservableCollection Following code can be used:
fulllist = new ObservableCollection<NewsData>(new nList());
添加用于从fulllist删除数据的实现，可能的实现可能是:
Add the implementation for deleting data from fulllist a possible implementation could be:
object obj = lstNews.SelectedItem;
if(obj is NewsData){
fulllist.Remove((NewsData)obj);
lstNews.ItemsSource = fulllist;
}
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