c# How can I expand an item within a ListView to occupy multiple lines?

<ListBox ItemsSource="{Binding}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <Grid>
                    <Grid.RowDefinitions>
                        <RowDefinition></RowDefinition>
                        <RowDefinition></RowDefinition>
                    </Grid.RowDefinitions>

                    <Grid Grid.Row="0" Height="20" >
                        <TextBlock Text="Not Selected"></TextBlock>
                    </Grid>
                    <Grid x:Name="selectedOnlyGrid" Grid.Row="1" Visibility="Collapsed">
                        <TextBlock Text="Selected"></TextBlock>
                    </Grid>

                </Grid>

                <DataTemplate.Triggers>
                    <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBoxItem}, AncestorLevel=1}, Path=IsSelected}" Value="True">
                        <Setter Property="Visibility" Value="Visible" TargetName="selectedOnlyGrid" />
                    </DataTrigger>
                </DataTemplate.Triggers>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>