ICollectionView 过滤器影响源答案

【问题标题】：ICollectionView filter affects the sourceICollectionView 过滤器影响源
【发布时间】：2013-04-29 18:38:48
【问题描述】：

我在试验 WPF 时遇到了一些我没有预料到的过滤行为。

我用 ListView 和 DataGrid 创建了一个简单的 Window 控件，它显示有关美国总统的信息，例如姓名、政党和数字顺序。

应用程序实例化一个带有多个总统的 ObservableCollection。在 Main 中，从 ObservableCollection 创建一个视图，并应用过滤和排序。 ListView 绑定到这个视图，DataGrid 绑定到原来的 ObservableCollection。

我希望 ListView 显示过滤后的结果，而 DataGrid 显示列表中的所有项目。但是，DataGrid 也会显示过滤后的结果。有人对此有解释吗？

public partial class MainWindow : Window
{
    ICollectionView presidentView;

    ObservableCollection<President> presidents = new ObservableCollection<President>
    {
        new President{Name = "Barack Obama", Party="Democratic", Order=44},
        new President {Name = "George W Bush", Party="Republican", Order=43},
        new President{Name = "Bill Clinton", Party="Democratic", Order=42},
        new President {Name="George Bush", Party="Republican", Order=41},
        new President{Name="Ronald Reagan", Party="Republican", Order=40},
        new President{Name="Jimmy Carter", Party="Democratic", Order=39},
        new President{Name="Gerald Ford", Party="Republican", Order=38},
        new President{Name="Richard Nixon", Party="Republican", Order=37},
        new President{Name="Lyndon Johnson", Party="Democratic", Order=36}
    };


    public MainWindow()
    {
        InitializeComponent();

        presidentView = CollectionViewSource.GetDefaultView(presidents);
        presidentView.SortDescriptions.Add(new SortDescription("Order", ListSortDirection.Ascending));

        Predicate<object> isRepublican = (x) => 
        {
            President p = x as President;
            return p.Party == "Republican";
        };

        presidentView.Filter = isRepublican;

        list.ItemsSource = presidentView;
        grid.ItemsSource = presidents;
    }
}

public class President
{
    public int Order { set; get; }
    public string Name { set; get; }
    public string Party { set; get; }
}


<Window x:Class="WpfApplication2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication2"
        Title="MainWindow" Height="350" Width="727.416">
    <Grid>
        <ListView HorizontalAlignment="Left" Height="260" Margin="10,10,0,0" Name="list" VerticalAlignment="Top" Width="197">
            <ListView.ItemTemplate>
                <ItemContainerTemplate>
                    <TextBlock Text="{Binding Path=Name}">                        
                    </TextBlock>
                </ItemContainerTemplate>
            </ListView.ItemTemplate>
        </ListView>
        <DataGrid Name="grid" HorizontalAlignment="Left" Margin="224,13,0,0" VerticalAlignment="Top" Height="257" Width="487"/>
    </Grid>
</Window>

【问题讨论】：

标签： wpf data-binding icollectionview

【解决方案1】：

您可以通过创建ICollectionView 的新实例来解决此问题，供您希望独立于其他控件的每个控件使用（通常，每个不同的过滤器使用不同的实例）。

更新您的 presidentView 以像这样实例化：

public MainWindow()
{
    InitializeComponent();

    presidentView = new CollectionViewSource { Source= presidents }.View;
    presidentView.SortDescriptions.Add(new SortDescription("Order", ListSortDirection.Ascending));

    Predicate<object> isRepublican = (x) =>
    {
        President p = x as President;
        return p.Party == "Republican";
    };
    presidentView.Filter = isRepublican;

    list.ItemsSource = presidentView;
    grid.ItemsSource = presidents;
}

【讨论】：