SelectedValuesListBox - A ListBox that implements more than one SelectedValue (SelectedValues)

<Window x:Class="Sandrino.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:Sandrino"
    Title="Window1" Height="419" Width="868">
    <Grid>
        <local:SelectedValuesListBox ItemsSource="{Binding Path=Languages}"
            SelectedValues="{Binding Path=Me.LanguageIDs}"
            SelectedValuePath="ID" Margin="12,53,322,12" x:Name="listLanguages" SelectionMode="Multiple">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <Label Content="{Binding Name}" FontWeight="Bold"/>
                            <Label Content="{Binding ID}" FontStyle="Italic"/>
                        </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
        </local:SelectedValuesListBox>
        
        <TextBlock Height="21" HorizontalAlignment="Left" Margin="12,26,0,0" Name="textBlock1" VerticalAlignment="Top" Width="161">List</TextBlock>
        <ListBox ItemsSource="{Binding ElementName=listLanguages, Path=SelectedValues}" Margin="0,53,12,12" Name="listSelection" HorizontalAlignment="Right" Width="304" />
        <TextBlock Height="21" Margin="0,26,155,0" Name="textBlock2" VerticalAlignment="Top" Text="Selection" HorizontalAlignment="Right" Width="161"></TextBlock>
        <Button Height="23" HorizontalAlignment="Right" Margin="0,12,12,0" Name="button1" VerticalAlignment="Top" Width="114" Click="button1_Click">Show my languages</Button>
    </Grid>
</Window>