WPF 过滤列表框答案

【问题标题】：WPF Filter a ListBoxWPF 过滤列表框
【发布时间】：2022-03-17 02:14:12
【问题描述】：

我有一个绑定到字符串列表的ListBox。我想在TextBox 中输入文本时过滤列表。我该怎么做？

public void ListLoad()
{
    ElementList = new List<string>(); // creation a list of strings
    ElementList.Add("1"); // add a item of string
    ElementList.Add("2"); // add a item of string

    DataContext = this; // set the data context
}

我在 XAML 中绑定它：

ItemsSource="{Binding ElementList}"

【问题讨论】：

标签： c# wpf list xaml listbox

【解决方案1】：

CollectionViewSource 类可以在这里提供帮助。据我所知，它具有许多过滤、排序和分组集合的功能。

ICollectionView view = CollectionViewSource.GetDefaultView(ElementList);
view.Filter = (o) => {return o;}//here is the lambda with your conditions to filter

当您不需要任何过滤器时，只需将view.Filter 设置为null。另请查看filtering上的这篇文章

【讨论】：

【解决方案2】：

这是一个用于绑定过滤器的附加属性：

using System;
using System.Windows;
using System.Windows.Controls;

public static class Filter
{
    public static readonly DependencyProperty ByProperty = DependencyProperty.RegisterAttached(
        "By",
        typeof(Predicate<object>),
        typeof(Filter),
        new PropertyMetadata(default(Predicate<object>), OnByChanged));

    public static void SetBy(ItemsControl element, Predicate<object> value)
    {
        element.SetValue(ByProperty, value);
    }

    public static Predicate<object> GetBy(ItemsControl element)
    {
        return (Predicate<object>)element.GetValue(ByProperty);
    }

    private static void OnByChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is ItemsControl itemsControl &&
            itemsControl.Items.CanFilter)
        {
            itemsControl.Items.Filter = (Predicate<object>)e.NewValue;
        }
    }
}

在 xaml 中这样使用：

<DataGrid local:Filter.By="{Binding Filter}"
          ItemsSource="{Binding Foos}">
    ...

和视图模型：

public class ViewModel : INotifyPropertyChanged
{
    private string filterText;
    private Predicate<object> filter;

    public event PropertyChangedEventHandler PropertyChanged;

    public ObservableCollection<Foo> Foos { get; } = new ObservableCollection<Foo>();

    public string FilterText
    {
        get { return this.filterText; }
        set
        {
            if (value == this.filterText) return;
            this.filterText = value;
            this.OnPropertyChanged();
            this.Filter = string.IsNullOrEmpty(this.filterText) ? (Predicate<object>)null : this.IsMatch;
        }
    }

    public Predicate<object> Filter
    {
        get { return this.filter; }
        private set
        {
            this.filter = value;
            this.OnPropertyChanged();
        }
    }

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

    private bool IsMatch(object item)
    {
        return IsMatch((Foo)item, this.filterText);
    }

    private static bool IsMatch(Foo item, string filterText)
    {
        if (string.IsNullOrEmpty(filterText))
        {
            return true;
        }

        var name = item.Name;
        if (string.IsNullOrEmpty(name))
        {
            return false;
        }

        if (filterText.Length == 1)
        {
            return name.StartsWith(filterText, StringComparison.OrdinalIgnoreCase);
        }

        return name.IndexOf(filterText, 0, StringComparison.OrdinalIgnoreCase) >= 0;
    }
}

【讨论】：

【解决方案3】：

如果您将 Dictionary 设置为 itemsource 到列表框，请使用以下代码进行排序，

    private void tb_filter_textChanged(object sender, TextChangedEventArgs e)
    {
        Dictionary<string, string> dictObject = new Dictionary<string, string>();
        ICollectionView view = CollectionViewSource.GetDefaultView(dictObject);
        view.Filter = CustomerFilter;
        listboxname.ItemsSource = view;
    }

    private bool CustomerFilter(object item)
    {
        KeyValuePair<string, string> Items = (KeyValuePair<string,string>) item;
        return Items.Value.ToString().Contains("a");
    }

以上代码返回包含“a”的项目。

【讨论】：