Does MultiSelectionComboBox support grouping?

[Filipsi]

Does MultiSelectionComboBox support item grouping and GroupStyle?
When I set ItemsSource to a CollectionViewSource, the control ends up in custom text state even trough IsEditable is set to false.

<UserControl.Resources>
    <CollectionViewSource
        x:Key="GroupedAvailableTargets"
        Source="{Binding AvailableTargets}">

        <CollectionViewSource.GroupDescriptions>
            <PropertyGroupDescription PropertyName="Category" />
        </CollectionViewSource.GroupDescriptions>
    </CollectionViewSource>
</UserControl.Resources>

<mah:MultiSelectionComboBox
    mah:MultiSelectorHelper.SelectedItems="{Binding SelectedTargets}"
    ItemContainerStyle="{StaticResource MahApps.Styles.MultiSelectionComboBoxItem.CheckBox}"
    ItemsSource="{Binding Source={StaticResource GroupedAvailableTargets}}"
    SelectionMode="Multiple">

[timunie]

That is a really good question. I think it doesn't support it out of the box, but probably it can be added quite easily. For now, I'd suggest to copy the original Style and add grouping to the ListBox inside the PopUp:

MahApps.Metro/src/MahApps.Metro/Themes/MultiSelectionComboBox.xaml

Lines 461 to 476 in 3fce022

	<ListBox x:Name="PART_PopupListBox"
	Grid.Row="1"
	AlternationCount="{TemplateBinding AlternationCount}"
	Focusable="False"
	ItemContainerStyle="{TemplateBinding ItemContainerStyle}"
	ItemContainerStyleSelector="{TemplateBinding ItemContainerStyleSelector}"
	ItemStringFormat="{TemplateBinding ItemStringFormat}"
	ItemTemplate="{TemplateBinding ItemTemplate}"
	ItemTemplateSelector="{TemplateBinding ItemTemplateSelector}"
	ItemsSource="{TemplateBinding ItemsSource}"
	SelectedIndex="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}, Path=SelectedIndex, Mode=TwoWay}"
	SelectedItem="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}, Path=SelectedItem, Mode=TwoWay}"
	SelectedValue="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}, Path=SelectedValue, Mode=TwoWay}"
	SelectedValuePath="{TemplateBinding SelectedValuePath}"
	SelectionMode="{TemplateBinding SelectionMode}"
	SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />

Good luck 👍