Question

我有一个视图模型，该模型公开了ListCollectionView和与其绑定的数据网格。出于某些原因，当交换ListCollectionView并从源集合中创建一个新项目时，对于添加到源集合中的新项目的排序会丢失。

源集合是一个ObservableCollection。对于创建ListCollectionView时源集合中已经存在的项目，排序是正确的。我不使用GetDefaultView，而是在需要时自己创建ListCollectionView。将新项目添加到源集合时，不会进行排序，并且项目会显示在列表的末尾。交换ListCollectionView时会引发INotifyPropertyChanged。

有人知道我为什么会这样吗？

Answer 1

问题可能出在您创建listcollectionview的过程中。（您应该已经发布了该代码。）

我将一些实验代码放在一起，可以按预期工作。我只使用一个列表框，但这没什么区别。

<Window.DataContext>
    <local:MainWindowViewModel/>
</Window.DataContext>
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="100"/>
    </Grid.ColumnDefinitions>
    <Button Command="{Binding AddPersonCommand}" Grid.Column="1"/>
    <ListBox ItemsSource="{Binding People}"
             >
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding LastName}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

Viewmodel

public class MainWindowViewModel : BaseViewModel
{
    private RelayCommand addPersonCommand;
    public RelayCommand AddPersonCommand
    {
        get
        {
            return addPersonCommand
            ?? (addPersonCommand = new RelayCommand(
              () =>
             {
                 People.Add(new Person { FirstName = "Adam", LastName = "Barlow" });
             }
             ));
        }
    }
    private ObservableCollection<Person> people = new ObservableCollection<Person>();

    public ObservableCollection<Person> People
    {
        get { return people; }
        set { people = value; }
    }


    public ListCollectionView LCV { get; set; }
    public MainWindowViewModel()
    {
        LCV = (ListCollectionView)CollectionViewSource.GetDefaultView(People);
        LCV.SortDescriptions.Add(
            new SortDescription("LastName", ListSortDirection.Ascending));
        People.Add(new Person { FirstName = "Chesney", LastName = "Brown" });
        People.Add(new Person { FirstName = "Gary", LastName = "Windass" });
        People.Add(new Person { FirstName = "Liz", LastName = "McDonald" });
        People.Add(new Person { FirstName = "Carla", LastName = "Connor" });
    }
}

当我单击按钮时，它将Ken Barlow添加到observablecollection中，并且它出现在列表框的顶部。

我也尝试绑定到LCV：

并实例化通过ctor传入的人。

public class MainWindowViewModel : BaseViewModel
{
    private RelayCommand addPersonCommand;
    public RelayCommand AddPersonCommand
    {
        get
        {
            return addPersonCommand
            ?? (addPersonCommand = new RelayCommand(
              () =>
              {
                  Person person = new Person { FirstName = "Adam", LastName = "Barlow" };
                  People.Add(person);
              }
             ));
        }
    }

    private ObservableCollection<Person> people = new ObservableCollection<Person>();

    public ObservableCollection<Person> People
    {
        get { return people; }
        set { people = value; }
    }

    public ListCollectionView LCV { get; set; }
    public MainWindowViewModel()
    {
        People.Add(new Person { FirstName = "Chesney", LastName = "Brown" });
        People.Add(new Person { FirstName = "Gary", LastName = "Windass" });
        People.Add(new Person { FirstName = "Liz", LastName = "McDonald" });
        People.Add(new Person { FirstName = "Carla", LastName = "Connor" });
        LCV = new ListCollectionView(People);
        LCV.SortDescriptions.Add(
            new SortDescription("LastName", ListSortDirection.Ascending));
    }
}

这也可以。

DataGrid ListCollectionView排序

1 个答案: