Filtering a ComboBox with a GroupStyle

Question

I have a Telerik ComboBox which has a GroupStyle applied to it. I want to have it so that when the items are filtered, the group items disappear if they have no children items, and it continues up the hierarchy.

So, this is the initial setup:

Current:

Desired:

For reference:

GroupItem Style

<Style TargetType="{x:Type GroupItem}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate>
                <Expander Header="{Binding Path=Name}">
                    <ItemsPresenter Margin="20,0,0,0" />
                </Expander>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
    <Style.Triggers>
        <DataTrigger
            Binding="{Binding Path=Name}"
            Value="{x:Null}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate>
                        <ItemsPresenter />
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </DataTrigger>
    </Style.Triggers>
</Style>

RadComboBox

<telerik:RadComboBox
    Grid.Column="1"
    DisplayMemberPath="Name"
    IsEditable="True"
    IsFilteringEnabled="True"
    ItemsSource="{Binding Path=Analyzers}"
    KeyboardNavigation.TabNavigation="Local"
    OpenDropDownOnFocus="True"
    SelectedItem="{Binding Path=Analyzer, Mode=OneWayToSource}"
    SelectedValue="{Binding Path=AnalyzerId, Converter={utilities:NullToZeroValueConverter}}"
    SelectedValuePath="Id"
    Style="{StaticResource ResourceKey=RadComboBoxStyle.CanDisable}"
    TabIndex="2">
    <telerik:RadComboBox.ItemContainerStyle>
        <Style
            BasedOn="{StaticResource ResourceKey=RadComboBoxItemStyle}"
            TargetType="telerik:RadComboBoxItem">
            <Setter Property="ToolTip" Value="{Binding Path=Description}" />
        </Style>
    </telerik:RadComboBox.ItemContainerStyle>
    <telerik:RadComboBox.GroupStyle>
        <GroupStyle />
    </telerik:RadComboBox.GroupStyle>
</telerik:RadComboBox>       

Answer 1

I found the following (related) example on the Telerik forums. Example