Question

我使用List来绑定一个列表框，如下所示：

<ListBox x:Name="ContentPanel" SelectionChanged="onSelectionChanged" Background="LightGray" Grid.Row="2">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <Grid Name="{Binding title}" Height="165" Margin="25,5,25,0" Width="430">
                    <Border BorderThickness="1"   Height="165"  BorderBrush="Gray">
                        <toolkit:ContextMenuService.ContextMenu >
                            <toolkit:ContextMenu IsZoomEnabled="False">
                                <toolkit:MenuItem Name="Delete" Header="Delete Message" Click="DeleteMessage_Click"  >

                                </toolkit:MenuItem>
                            </toolkit:ContextMenu>
                        </toolkit:ContextMenuService.ContextMenu>
                        <StackPanel Orientation="Vertical">
                            <StackPanel>
                                <TextBlock Text="{Binding title}" Margin="5,0,0,0" FontSize="25" Foreground="Black"/>
                                <TextBlock Text="{Binding msgFrom}" Padding="5" TextWrapping="Wrap" Foreground="Gray" FontSize="20"/>

                            </StackPanel>

                            <StackPanel Orientation="Horizontal">
                                <TextBlock  Margin="5,13,0,0" FontSize="24" Foreground="WhiteSmoke" Text="{Binding msgReceivedOn}"/>
                                <toolkit:ToggleSwitch Margin="170,10,0,0" IsChecked="{Binding msgStatus}" Unchecked="UnChecked"  Background="LightBlue" Checked="Checked"/>
                            </StackPanel>
                        </StackPanel>
                    </Border>
                </Grid>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>

首先成功加载数据。但是当我使用Contextmenu删除项目并重新加载列表框时...它会触发异常。处理上下文菜单单击的代码是：

private void DeleteMessage_Click(object sender, RoutedEventArgs e)
    {
        MenuItem item = sender as MenuItem;
        Message message = (Message)item.DataContext;
        MessageBoxResult result = MessageBox.Show("Are you sure to delete the message??", "Confirmation", MessageBoxButton.OKCancel);
        if (result == MessageBoxResult.Cancel)
            return;      

 else
        {
           ContentPanel.Items.Remove(message);
             lstMessage.Remove(message);
        }
            ContentPanel.ItemSource = lstMessage;
    }

但是这段代码不起作用。那么有什么建议吗？

Answer 1

您不需要每次都将集合绑定到列表。此外，当您从集合中删除项目时，它也应该在列表中消失（如果绑定设置正确）。我认为你没有ObservableCollection，所以你需要手动管理项目。请考虑使用ObservableCollection。

您的代码应如下所示：

 lstMessage.Remove(message); //it must raises CollectionChanged event automatically

这条线是不必要的：

 ContentPanel.Items.Remove(message);

 ContentPanel.ItemSource = lstMessage;

在WP7中重新加载列表框

1 个答案: