Question

我有ListBox根据文本框中输入的文字过滤项目（按下输入时）：

<TextBox DockPanel.Dock="Top" Margin="0,0,0,20" Width="200" HorizontalAlignment="Left" Text="{Binding Path=FilterText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
   <TextBox.InputBindings>
      <KeyBinding Command="{Binding Path=FilterSearchCommand}" Key="Enter" />
   </TextBox.InputBindings>
</TextBox>
<ListBox DockPanel.Dock="Bottom" Name="lbItems" ItemsSource="{Binding Path=MyList, UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Stretch">
   <ListBox.ItemTemplate>
      <DataTemplate>
         <StackPanel Width="{Binding ActualWidth, ElementName=lbItems}" Cursor="Hand" Margin="10,10,0,10" VerticalAlignment="Center" MouseLeftButtonUp="UIElement_OnMouseLeftButtonUp">
            <TextBlock Text="{Binding Path=Title}"/>
         </StackPanel>
      </DataTemplate>
   </ListBox.ItemTemplate>
</ListBox>

在文本框中按下ENTER时，将执行以下命令：

FilterSearchCommand = new RelayCommand(() => {
 MyList = new ObservableCollection < MyObject > (MyList.Where(x => x.Title.IndexOf(FilterText, StringComparison.InvariantCultureIgnoreCase) >= 0).ToList());
});

public RelayCommand FilterSearchCommand {
 get;
}
public string FilterText {
 get;
 set;
}
public ObservableCollection < MyObject > MyList {
 get;
 set;
}

基本上在输入命令时，ObservableCollection已成功更新，但列表框中的项目保持不变。

有什么想法吗？

Answer 1

这里你会遇到一些问题 - 搜索后，你将覆盖你的'MyList'对象。因此，一旦过滤，就无法取消过滤。您应该考虑使用CollectionViewSource。

Answer 2

您需要实现INotifyPropertyChanged，并且在MyList的setter中，您将通知UI该属性已更改。这是一个例子：

class MyViewModel : INotifyPropertyChanged
{
    private ObservableCollection<MyObject> _myList;

    public ObservableCollection<MyObject> MyList
    {
        get { return _myList; }
        set
        {
            _myList = value; 
            OnPropertyChanged();
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

当项目添加到数据源时，ListBox未更新

2 个答案: