Grouping items disregards items style ( Groups show up empty )

Question

This is basically a follow up question to my previous question found here

I'm trying to group items in a combobox but my problem is that either the GroupDescription is shown or the items.

If I add collectionView.GroupDescriptions.Add(new PropertyGroupDescription("Team")); then my ComboBoxItem style will be disregarded (it never gets to a breakpoint). Why is that?

I've checked the collectionView and it contais 3 groups with 2 items in each as it should. But the dropdown only shows the "grouping name" (i.e. team name).

******EDIT******

The problem seems to be in my ComboBoxStyle since removing it makes life wonderful...

<Style x:Key="ImageComboBox" BasedOn="{StaticResource {x:Type ComboBox}}" TargetType="{x:Type ComboBox}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ComboBox">
                    <Grid>
                        <ToggleButton Name="ToggleButton" Template="{StaticResource ComboBoxToggleButton}" Grid.Column="2" Focusable="false" IsChecked="{Binding Path=IsDropDownOpen,Mode=TwoWay,RelativeSource={RelativeSource TemplatedParent}}" ClickMode="Press"/>
                        <ContentPresenter Name="ContentSite" IsHitTestVisible="False" Content="{TemplateBinding SelectionBoxItem}" ContentTemplate="{StaticResource DisplayImageWithText}" ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}" Margin="3,3,23,3" VerticalAlignment="Center" HorizontalAlignment="Left"/>
                        <TextBox x:Name="PART_EditableTextBox" Style="{x:Null}" Template="{StaticResource ComboBoxTextBox}" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="3,3,23,3" Focusable="True" Background="Transparent" Visibility="Hidden" IsReadOnly="{TemplateBinding IsReadOnly}"/>
                        <Popup Name="Popup" Placement="Bottom" IsOpen="{TemplateBinding IsDropDownOpen}" AllowsTransparency="True" Focusable="False" PopupAnimation="Slide">
                            <Grid Name="DropDown" SnapsToDevicePixels="True" MinWidth="{TemplateBinding ActualWidth}" MaxHeight="{TemplateBinding MaxDropDownHeight}">
                                <Border x:Name="DropDownBorder" Background="{StaticResource WindowBackgroundBrush}" BorderThickness="1" BorderBrush="{StaticResource SolidBorderBrush}"/>
                                <ScrollViewer Margin="4,6,4,6" SnapsToDevicePixels="True">
                                    <Grid x:Name="itemsGrid" Height="Auto" Width="Auto" MaxWidth="{TemplateBinding MaxWidth}">
                                        <StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Contained"/>
                                    </Grid>
                                </ScrollViewer>
                            </Grid>
                        </Popup>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="HasItems" Value="false">
                            <Setter TargetName="DropDownBorder" Property="MinHeight" Value="95"/>
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}"/>
                        </Trigger>
                        <Trigger Property="IsGrouping" Value="true">
                            <Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
                        </Trigger>
                        <Trigger SourceName="Popup" Property="Popup.AllowsTransparency" Value="true">
                            <Setter TargetName="DropDownBorder" Property="CornerRadius" Value="4"/>
                            <Setter TargetName="DropDownBorder" Property="Margin" Value="0,2,0,0"/>
                        </Trigger>
                        <Trigger Property="IsEditable" Value="true">
                            <Setter Property="IsTabStop" Value="false"/>
                            <Setter TargetName="PART_EditableTextBox" Property="Visibility" Value="Visible"/>
                            <Setter TargetName="ContentSite" Property="Visibility" Value="Hidden"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

Answer 1

I'm not sure what's causing your problems based on the information you provided above. But the code below, which is an update to the answer I gave on the link you specified, works fine for me:

Styles:

<Style x:Key="ComboBoxItemStyle" TargetType="ComboBoxItem">
    <Setter Property="Foreground" Value="Red"/>
</Style>

<Style x:Key="ComboBoxStyle" BasedOn="{StaticResource {x:Type ComboBox}}" TargetType="{x:Type ComboBox}">
    <Setter Property="ItemContainerStyle" Value="{StaticResource ComboBoxItemStyle}"/>
</Style>

ComboBox:

<ComboBox x:Name="comboBox" Style="{StaticResource ComboBoxStyle}">
    <ComboBox.GroupStyle>
        <GroupStyle>
            <GroupStyle.HeaderTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </GroupStyle.HeaderTemplate>
        </GroupStyle>
    </ComboBox.GroupStyle>
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Name}"/>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

Hope this will help you solve your problem.