Here is an attached property for binding a filter:
using System;
using System.Windows;
using System.Windows.Controls;
public static class Filter
{
public static readonly DependencyProperty ByProperty = DependencyProperty.RegisterAttached(
"By",
typeof(Predicate),
typeof(Filter),
new PropertyMetadata(default(Predicate), OnByChanged));
public static void SetBy(ItemsControl element, Predicate value)
{
element.SetValue(ByProperty, value);
}
public static Predicate GetBy(ItemsControl element)
{
return (Predicate)element.GetValue(ByProperty);
}
private static void OnByChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (d is ItemsControl itemsControl &&
itemsControl.Items.CanFilter)
{
itemsControl.Items.Filter = (Predicate)e.NewValue;
}
}
}
Used like this in xaml:
...
And viewmodel:
public class ViewModel : INotifyPropertyChanged
{
private string filterText;
private Predicate filter;
public event PropertyChangedEventHandler PropertyChanged;
public ObservableCollection Foos { get; } = new ObservableCollection();
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)null : this.IsMatch;
}
}
public Predicate 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;
}
}
加载中...