How to do Expand/Collapse for MultiParent Layout in WPF Diagram(SfDiagram)?

 
ObservableCollection<object> SelectedNodeCollection => (sfdiagram.SelectedItems as SelectorViewModel)?.Nodes as ObservableCollection<object>;
 
private ObservableCollection<NodeViewModel> NodeCollection => sfdiagram.Nodes as ObservableCollection<NodeViewModel>;
 
public ObservableCollection<ItemInfo> AllCards => sfdiagram.DataSourceSettings.DataSource as ObservableCollection<ItemInfo>;
 
private ObservableCollection<ConnectorVM> ConnectorsCollection => sfdiagram.Connectors as ObservableCollection<ConnectorVM>;
private void ExpandCollapse_Click(object sender, RoutedEventArgs e)
{
    var workingCollection = SelectedNodeCollection;
    var selectednode = (sfdiagram.SelectedItems as SelectorViewModel).SelectedItem;
    ItemInfo obj = null;
    if(selectednode != null && selectednode is NodeViewModel)
    {
        obj = (ItemInfo)(selectednode as NodeViewModel).Content;
    }
 
    if (obj != null)
    {
        workingCollection = new ObservableCollection<object> 
        {
            NodeCollection.FirstOrDefault(j => j.Content == obj) 
        };
    }
    if (workingCollection.Count <= 0) return;
    //Multiple Nodes can be selected, and their child node can be collapsed/expanded at the same time
    foreach (NodeViewModel selectedItem in workingCollection)
    {
        var expandCollapseParameter = new ExpandCollapseParameter
        {
            Node = selectedItem,
            IsUpdateLayout = true
        };
        var graphInfo = sfdiagram.Info as IGraphInfo;
        // Without this get operation, the IsExpanded property of the node is not updated.
        var isExpanded = selectedItem.IsExpanded; 
        graphInfo?.Commands.ExpandCollapse.Execute(expandCollapseParameter);
 
        var currentCardTree = new List<ItemInfo>();
        var content = selectedItem.Content as ItemInfo;
        currentCardTree.AddRange(FindChildren(AllCards.ToList(), content));
 
        var childNodes = NodeCollection.Where(j => currentCardTree.Contains(j.Content)).ToList();
        var childConnectors = ConnectorsCollection.Where(j => childNodes.Contains(j.TargetNode)).ToList();
        childConnectors.ForEach(j => j.IsVisible = !isExpanded);
    }
}private List<ItemInfo> FindChildren(List<ItemInfo> source, ItemInfo root)
{
    return source.Where(j => j.ReportingPerson.Contains(root.Name))
        .Union(source.Where(j => j.ReportingPerson.Contains(root.Name)).SelectMany(j => FindChildren(source, j)))
        .ToList();
}