Show element only when selected and only when is not empty

Question

I am in a similar case that this question: Displaying Content only when ListViewItem is Selected

I have a ComboBox that I only want to show when the ListViewItem that contains it is selected and when the ComboBox is not empty (both conditions must be true). It is very easy to bind visibility to a readonly property that checks if the ItemsSource property in the ViewModel has any items, and with the above link it is also solved how to show it only when its ListViewItem is selected, but I am not able to join both conditions. How can I only show the ComboBox when the item is selected and the combo is not empty?

This Style in the ComboBox does the trick for showing only when is selected:

<ComboBox ItemsSource="{Binding DataContext.ListaPedidosPendientes, RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl}}" DisplayMemberPath="numero">
    <ComboBox.Style>
        <Style TargetType="{x:Type ComboBox}">
            <Setter Property="Visibility" Value="Collapsed"/>
            <Style.Triggers>
                <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor,
                    AncestorType={x:Type ListBoxItem}},Path=IsSelected}" Value="True">
                    <Setter Property="Visibility" Value="Visible"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </ComboBox.Style>
</ComboBox>

How can I add there the second condition (ListaPedidosPendientes.Count > 0)?

Thank you

Answer 1

You can evaluate the HasItems property of the ComboBox https://learn.microsoft.com/en-us/dotnet/api/system.windows.controls.itemscontrol.hasitems?view=net-5.0 and invert the conditions: Visible by default, collapse when not selected or when no items. Untested Aircode:

<ComboBox ItemsSource="{Binding DataContext.ListaPedidosPendientes, RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl}}" DisplayMemberPath="numero">
    <ComboBox.Style>
        <Style TargetType="{x:Type ComboBox}">
            <Setter Property="Visibility" Value="Visible"/>
            <Style.Triggers>
                <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor,
                    AncestorType={x:Type ListBoxItem}},Path=IsSelected}" Value="False">
                    <Setter Property="Visibility" Value="Collapsed"/>
                </DataTrigger>
                <Trigger Property="HasItems" Value="False">
                    <Setter Property="Visibility" Value="Collapsed"/>
                </Trigger>
            </Style.Triggers>
        </Style>
    </ComboBox.Style>
</ComboBox>