Улучшения производительности Combobox Silverlight, уже использующие виртуализацию

Я работаю с комбинированным списком, чтобы показать список элементов с флажком. Проблема, с которой я столкнулся, заключается в том, что производительность при отображении (рендеринге, я думаю) списка элементов при открытии списка со списком замедляется при увеличении количества элементов (например, 300 элементов занимают около 3 секунд, и мне нужно будет показать 1000) .

Вот как выглядит код:

MultiSelComboBoxStyle.xaml

    <ResourceDictionary
    xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x = "http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d = "http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc = "http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:System = "clr-namespace:System;assembly=mscorlib">

    <Style x:Key = "CheckBoxListBoxItemStyle" TargetType = "ListBoxItem">
        <Setter Property = "Template">
            <Setter.Value>
                <ControlTemplate TargetType = "ListBoxItem">
                    <Grid x:Name = "RootElement">
                        <!--<CheckBox ClickMode = "Press" Content = "{Binding Path=Name}" IsChecked = "{Binding Path=IsSelected, Mode=TwoWay}" />-->
                        <CheckBox IsChecked = "{Binding IsChecked, Mode=TwoWay}" Content = "{Binding Text}" />
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style x:Key = "MSMMultiSelComboBoxStyle" TargetType = "ComboBox">
        <Setter Property = "Padding" Value = "6,2,25,2"/>
        <Setter Property = "HorizontalContentAlignment" Value = "Left"/>
        <Setter Property = "BorderThickness" Value = "1"/>
        <Setter Property = "TabNavigation" Value = "Once"/>
        <Setter Property = "ScrollViewer.HorizontalScrollBarVisibility" Value = "Auto"/>
        <Setter Property = "ScrollViewer.VerticalScrollBarVisibility" Value = "Auto"/>

        <Setter Property = "Template">
            <Setter.Value>
                <ControlTemplate TargetType = "ComboBox">
                    <Grid>
                        <Border x:Name = "ContentPresenterBorder">
                            <Grid>
                                <ToggleButton x:Name = "DropDownToggle" HorizontalAlignment = "Stretch" HorizontalContentAlignment = "Right" Margin = "0" VerticalAlignment = "Stretch">
                                    <Path x:Name = "BtnArrow" Data = "F1 M 301.14,-189.041L 311.57,-189.041L 306.355,-182.942L 301.14,-189.041 Z " HorizontalAlignment = "Right" Height = "4" Margin = "0,0,6,0" Stretch = "Uniform" Width = "8">
                                        <Path.Fill>
                                            <SolidColorBrush x:Name = "BtnArrowColor" Color = "#FF333333"/>
                                        </Path.Fill>
                                    </Path>
                                </ToggleButton>
                                <ContentPresenter x:Name = "ContentPresenter" HorizontalAlignment = "{TemplateBinding HorizontalContentAlignment}" Margin = "{TemplateBinding Padding}" VerticalAlignment = "{TemplateBinding VerticalContentAlignment}">
                                    <TextBlock x:Name = "tb" Text = " "/>
                                </ContentPresenter>
                            </Grid>
                        </Border>
                        <Rectangle x:Name = "DisabledVisualElement" IsHitTestVisible = "false" Opacity = "0" RadiusY = "3" RadiusX = "3"/>
                        <Rectangle x:Name = "FocusVisualElement" IsHitTestVisible = "false" Margin = "1" Opacity = "0" RadiusY = "2" RadiusX = "2" StrokeThickness = "1"/>
                        <Border x:Name = "ValidationErrorElement" BorderThickness = "1" CornerRadius = "1" Visibility = "Collapsed">
                            <ToolTipService.ToolTip>
                                <ToolTip x:Name = "validationTooltip" DataContext = "{Binding RelativeSource = {RelativeSource TemplatedParent}}" Placement = "Right" PlacementTarget = "{Binding RelativeSource = {RelativeSource TemplatedParent}}" >
                                    <ToolTip.Triggers>
                                        <EventTrigger RoutedEvent = "Canvas.Loaded">
                                            <BeginStoryboard>
                                                <Storyboard>
                                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty = "IsHitTestVisible" Storyboard.TargetName = "validationTooltip">
                                                        <DiscreteObjectKeyFrame KeyTime = "0">
                                                            <DiscreteObjectKeyFrame.Value>
                                                                <System:Boolean>true</System:Boolean>
                                                            </DiscreteObjectKeyFrame.Value>
                                                        </DiscreteObjectKeyFrame>
                                                    </ObjectAnimationUsingKeyFrames>
                                                </Storyboard>
                                            </BeginStoryboard>
                                        </EventTrigger>
                                    </ToolTip.Triggers>
                                </ToolTip>
                            </ToolTipService.ToolTip>
                            <Grid Background = "Transparent" HorizontalAlignment = "Right" Height = "12" Margin = "1,-4,-4,0" VerticalAlignment = "Top" Width = "12">
                                <Path Data = "M 1,0 L6,0 A 2,2 90 0 1 8,2 L8,7 z" Margin = "1,3,0,0"/>
                                <Path Data = "M 0,0 L2,0 L 8,6 L8,8" Margin = "1,3,0,0"/>
                            </Grid>
                        </Border>
                        <Popup x:Name = "Popup">
                            <Border x:Name = "PopupBorder" BorderBrush = "{TemplateBinding BorderBrush}" BorderThickness = "{TemplateBinding BorderThickness}" CornerRadius = "3" HorizontalAlignment = "Stretch" Height = "Auto">
                                <Border.Background>
                                    <LinearGradientBrush EndPoint = "0.5,1" StartPoint = "0.5,0">
                                        <!--<GradientStop Color = "#FFFFFFFF" Offset = "0"/>
                                        <GradientStop Color = "#FFFEFEFE" Offset = "1"/>
                                    -->
                                    </LinearGradientBrush>
                                </Border.Background>
                                <ScrollViewer x:Name = "ScrollViewer" BorderThickness = "0" Padding = "1">
                                    <!--<ItemsPresenter/>-->
                                    <ListBox x:Name = "lstBox" SelectionMode = "Multiple" ItemsSource = "{TemplateBinding ItemsSource}" ItemContainerStyle = "{StaticResource CheckBoxListBoxItemStyle}" HorizontalAlignment = "Stretch" >
                                        <ListBox.ItemsPanel>
                                            <ItemsPanelTemplate>
                                                <VirtualizingStackPanel  />
                                            </ItemsPanelTemplate>
                                        </ListBox.ItemsPanel>
                                    </ListBox>
                                </ScrollViewer>
                            </Border>
                        </Popup>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</ResourceDictionary>

DeskCombo.xaml

<UserControl x:Class = "Apama.UI.Surveillance.Controls.DeskCombo"
    xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x = "http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d = "http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc = "http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable = "d"
    d:DesignHeight = "28" d:DesignWidth = "400">

    <UserControl.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source = "MultiSelComboBoxStyle.xaml"/>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </UserControl.Resources>

    <Grid x:Name = "LayoutRoot">
        <ComboBox x:Name = "cbDesk"  Grid.Row = "0" Grid.Column = "0" Style = "{StaticResource MSMMultiSelComboBoxStyle}" >
            <ComboBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <VirtualizingStackPanel />
                </ItemsPanelTemplate>
            </ComboBox.ItemsPanel>
        </ComboBox>
    </Grid>
</UserControl>

И вот как я привязываю элементы к комбинированному списку:

List<Desk> desks = new List<Desk>();

        desks.Add(new Desk() { DeskId = UIConstants.SELECT_ALL_TEXT, DeskName = UIConstants.SELECT_ALL_TEXT, DimDeskId = UIConstants.SELECT_ALL_ID });
        desks.AddRange(data.Desks.Values);

        _items = new StaticDataStore<Desk>(GetItemName, desks, AddAll);
        ComboBoxItems = new ComboBoxDataItemCollection(desks.Select(dk => new ComboBoxDataItem(dk.DimDeskId) { Text = dk.DeskName }));
        ComboBoxItems.Owner = this;

        // Bind
        cbDesk.ItemsSource = ComboBoxItems.ToList();

Я провел некоторое исследование и подумал, что это может быть связано с виртуализацией элементов, но я включил теги в список шаблонов стилей и в само поле со списком и не заметил никаких изменений.

Могу я еще что-нибудь проверить? Любая идея будет принята с благодарностью.