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POPerformance degredation with custom ListBox ControlTemplate
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  1. POPerformance degredation with custom ListBox ControlTemplate
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    copied!<p>Using a template for a custom control deriving from <code>ListBox</code> causes filtering of <code>ItemSource</code> to become slow. The filtering is done in the get of the <code>ItemSource</code> that the control is bound to. This problem is not present when a normal <code>ListBox</code> is used, so why should it be any different for a custom <code>ListBox</code>?</p> <p>Filtering:</p> <pre><code>public IEnumerable&lt;LibraryViewModel&gt; Libraries { get { if (!string.IsNullOrEmpty(this.LibrarySearchString)) return _libraries.Where(lib =&gt; IsLibraryMatch(lib, this.LibrarySearchString)); else return _libraries.OrderBy(lib =&gt; !lib.IsFavourite); } } </code></pre> <p>Using the control:</p> <pre><code>&lt;con:FilterListBox Grid.Row="1" ItemsSource="{Binding Libraries}" SelectedItem="{Binding SelectedLibrary}" ItemTemplate="{StaticResource LibraryItemTemplate}" SearchString="{Binding LibrarySearchString, Mode=TwoWay}" IsSearching="False" Margin="4"/&gt; </code></pre> <p>The control template:</p> <pre><code>&lt;Style x:Key="{x:Type con:FilterListBox}" TargetType="{x:Type con:FilterListBox}"&gt; &lt;Setter Property="Template"&gt; &lt;Setter.Value&gt; &lt;ControlTemplate TargetType="{x:Type con:FilterListBox}"&gt; &lt;Grid&gt; &lt;Grid.RowDefinitions&gt; &lt;RowDefinition Height="Auto"/&gt; &lt;RowDefinition/&gt; &lt;/Grid.RowDefinitions&gt; &lt;DockPanel Grid.Row="0"&gt; &lt;TextBlock Text="Search" VerticalAlignment="Center"/&gt; &lt;TextBox Text="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=SearchString, UpdateSourceTrigger=PropertyChanged}" Margin="4,0,0,0"/&gt; &lt;/DockPanel&gt; &lt;ScrollViewer Grid.Row="1" CanContentScroll="True"&gt; &lt;StackPanel IsItemsHost="True" HorizontalAlignment="Stretch"/&gt; &lt;/ScrollViewer&gt; &lt;TextBlock Grid.Row="1" Text="Searching..." HorizontalAlignment="Center" VerticalAlignment="Center" Visibility="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=IsSearching, Converter={StaticResource CollapsedIfFalseConverter}}"/&gt; &lt;/Grid&gt; &lt;/ControlTemplate&gt; &lt;/Setter.Value&gt; &lt;/Setter&gt; &lt;/Style&gt; </code></pre> <p>Thanks for any help.</p>
 

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