This control is an expandable ListView for the universal windows platform. It's a ported version of the expander for WPF which is not working properly on UWP. The repository is referenced here on StackOverflow.

• Add the project UWP_Expander (located in the folder ExpanderControl) to your solution and reference UWP_Expander from your project
• Reference the XAML Namespace

<Page xmlns:expander="using:Project.Views.Controls.ExpaControl">

• Setup ExpanderControl

• can be used as a ItemTemplate in a ListView see sample for more information

<expander:ExpanderControl
                        x:Name="expanderControl"
                        IsExpanded="False"
                        ItemsSource="{x:Bind ItemSource}"
                        IsNonExpandable="{x:Bind HasNoSubcategories}"
                        HeaderTemplate="{StaticResource HeaderTemplate}" 
                        ItemTemplate="{StaticResource ItemTemplate}"/>