<ComboBox
    SelectedItem="{Binding BlendMode, Mode=TwoWay}"
    ItemsSource="{Binding Source={StaticResource BlendMode}}">
</ComboBox>

private BlendMode _blendMode;
public BlendMode BlendMode
{
    get => _blendMode;
    set => SetAndNotify(ref _blendMode, value);
}

<ObjectDataProvider x:Key="BlendMode" MethodName="GetNames" ObjectType="{x:Type System:Enum}">
    <ObjectDataProvider.MethodParameters>
        <x:Type TypeName="ViewModels:BlendMode"/>
    </ObjectDataProvider.MethodParameters>
</ObjectDataProvider>

<ListBox
    ItemsSource="{Binding Layers}"
    SelectionMode="Single"
    dd:DragDrop.IsDragSource="True"
    dd:DragDrop.IsDropTarget="True">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <CMiX:ChannelLayer/>
        </DataTemplate>
    </ListBox.ItemTemplate>

public ObservableCollection<Layer> Layers { get; }