WPF ICollectionView筛选器重置 [英] WPF ICollectionView Filter Reset

问题描述

我有一个 CollectionView 源自 ObservableCollection ：

private static ObservableCollection<CalculationViewModel> _calculations;

CalculationViewModelsCollection = (CollectionView)CollectionViewSource.GetDefaultView(_calculations);

我的问题是，当过滤器的结果为空时，我想清除过滤器，并在其他条件下重新过滤，但 CollectionView 始终为空。

My problem is that, when the result of the filter is nothing, I'd like to clear the filter, and re-filter with other conditions, but the CollectionView is always empty.

我尝试重置过滤这些方式：

I tried to reset the filter these ways:

CalculationViewModelsCollection.Filter = null;
CalculationViewModelsCollection.Refresh();

和

CalculationViewModelsCollection.Filter = delegate(object p)
{
    return true;
};

但它们都不起作用。

您能否提供一些建议，如何在 CollectionView 上重置过滤器？

Could you give some advice how to reset a filter on a CollectionView?

推荐答案

从您的示例中，我不能完全确定您如何获取CollectionView，也不能确定我正确理解了您的问题。

From your example, I'm not entirely sure how you're getting your CollectionView, nor am I sure I understand your question correctly.

但是无论如何，我希望下面的示例代码可以帮助您解决问题。这是一个具有包含字符串的列表框和过滤器文本框的应用。如果列表中没有与过滤器匹配的内容，则过滤器将设置为null，从而显示所有项目。

But anyway, I hope the sample code below helps you with your problem. It's an app that has a listbox containing strings, and a "filter" textbox. if nothing in the list matches the filter, the filter will be set to null and thus display all items.

XAML：

<Window x:Class="WpfApplication3.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:v="clr-namespace:WpfApplication3"
        Title="MainWindow" Height="350" Width="525">
    <StackPanel>
        <TextBox x:Name="textBox" TextChanged="TextBox_TextChanged"/>        
        <ListBox x:Name="listBox"/>
    </StackPanel>
</Window>

代码隐藏：

public partial class MainWindow : Window
{
    ListCollectionView lcv;
    Predicate<object> filterFx;

    public MainWindow()
    {
        InitializeComponent();

        ObservableCollection<string> s = new ObservableCollection<string>();
        "The Quick Brown Fox Jumps Over The Lazy Dog"
            .Split(' ')
            .ToList()
            .ForEach((word) => s.Add(word.ToString()));

        this.lcv = new ListCollectionView(s);
        this.listBox.ItemsSource = this.lcv;

        this.filterFx = (p) => ((string)p).ToUpper().Contains(this.textBox.Text.ToUpper());
        lcv.Filter = this.filterFx;
    }

    private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
    {
        lcv.Refresh();

        if (lcv.Count == 0)
            lcv.Filter = null;
        else
            lcv.Filter = filterFx;
    }
}

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