Tukukkk

I have a user control with a textbox and a custom list control that's basically a ListBox with a CollectionView. I'd like to use the filter functionality of the CollectionView and use the text from the textbox to filter the visible elements.

A simplified representation of the xaml:

<TextBox x:Name="FilterTextControl"/>

<CustomControls:OverviewControl

    x:Name="ProfileOverviewControl"

    FilterText="{Binding ElementName=FilterTextControl, Path=Text, Mode=OneWay, Delay=5000}"

    Items="{Binding AllItems}"/>

The CollectionViewSource:

<CollectionViewSource x:Key="GroupedProfiles"

                  Source="{Binding Items, RelativeSource={RelativeSource AncestorType=local:OverviewControl}}"

                  Filter="GroupedProfiles_OnFilter">

<CollectionViewSource.SortDescriptions>

    <componentModel:SortDescription PropertyName="Location" />

    <componentModel:SortDescription PropertyName="Description" />

</CollectionViewSource.SortDescriptions>

    <CollectionViewSource.GroupDescriptions>

        <PropertyGroupDescription PropertyName="Location" />

    </CollectionViewSource.GroupDescriptions>

</CollectionViewSource>

The FilterText Dependency Property in the OverviewControl:

public string FilterText

{

    get => (string)GetValue(FilterTextProperty);

    set => SetValue(FilterTextProperty, value);

}



public static readonly DependencyProperty FilterTextProperty =

    DependencyProperty.Register(nameof(FilterText), typeof(string), 

    typeof(ProfileOverviewControl), new FrameworkPropertyMetadata(OnFilterTextChanged));



private static void OnFilterTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

{

     var intanceOfThisClass = (ProfileOverviewControl)d;

        if (_collectionViewSource == null) 

        _collectionViewSource = intanceOfThisClass.FindResource("GroupedProfiles") as CollectionViewSource;

     _collectionViewSource?.View?.Refresh();

}

The OnFilterEvent method:

    private void GroupedProfiles_OnFilter(object sender, FilterEventArgs e)

    {

        e.Accepted = string.IsNullOrEmpty(FilterText) || e.Item.ToString().Contains(FilterText);

    }

The Problem

As you can see in the binding of the FilterText I have a delay of 5000ms. For testing purposes I've made it 5000ms instead of a reasonable 500ms.
In order for the filter to work I need to refresh the CollectionView.
However the PropertyChangedCallback fires immediately after each change instead of throttling it with the delay binding.

I don't quite understand this behaviour. If this is just how a delay binding works, are there alternatives for throttling the CollectionView refresh?

Try reversing the bindings like this. This way the delay will be on the textbox change. Now the delay is on the filter property change (if changed from the OverviewControl).

<TextBox x:Name="FilterTextControl" Text="{Binding ElementName=ProfileOverviewControl, Path=FilterText, Delay=5000}"/>

<CustomControls:OverviewControl

    x:Name="ProfileOverviewControl"

    Items="{Binding AllItems}"/>