How to save the expandable state of LayoutGroup based on example in Q101774

UPDATED:
I've attached a complete WinForms sample to the How do I provide the capability to collapse or expand layout groups and persist their state? ticket (see its WinForms section for the main implementation steps). I hope you find this information helpful.
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Hello JeyKey,
I am afraid we do not have a ready example or guideline for this task. Technically, you can store the information about the expanded state in the application model. The state should be linked to the group's identifier or text.
To store some custom settings in the application model, create a custom model extension as described in the Extend and Customize the Application Model in Code article. Of course, you can use any other store for your custom settings here.

Hello Denis,

thanks for advice .
Here is the solution .

C#
//   ModelExtender.cs  

 public interface IModelLayoutGroupExtender  
 {  
        [DefaultValue(true)]  
        bool Expanded { get; set; }  
        [DefaultValue(false)]  
        bool Expandable { get; set; }  
        [DefaultValue(GroupElementLocation.Default)]  
        GroupElementLocation ExpandButtonLocation { get; set; }  
 }  

// Module.cs  

 public override void ExtendModelInterfaces(ModelInterfaceExtenders extenders) {  
          base.ExtendModelInterfaces(extenders);  
          extenders.Add<IModelLayoutGroup, IModelLayoutGroupExtender>();  
  }  

//ExpandableLayoutGroupViewController.cs  

    public partial class ExpandableLayoutGroupViewController : ViewController<DetailView>  
    {  
        Dictionary<string, IModelLayoutGroupExtender> layoutGroups = new Dictionary<string, IModelLayoutGroupExtender>();  

        public ExpandableLayoutGroupViewController()  
        {  
            InitializeComponent();  
            RegisterActions(components);  
            // Target required Views (via the TargetXXX properties) and create their Actions.  
        }  

        protected override void OnViewControlsCreated()  
        {  
            base.OnViewControlsCreated();  
            foreach (BaseLayoutItem item in ((LayoutControl)View.Control).Items)  
            {  
                if (item is LayoutControlGroup && layoutGroups.ContainsKey(item.Name))  
                {  
                    ((LayoutGroup)item).Expanded = layoutGroups[item.Name].Expanded;  
                    ((LayoutGroup)item).ExpandButtonLocation = layoutGroups[item.Name].ExpandButtonLocation;  
                    ((LayoutGroup)item).ExpandButtonVisible = true;  
                    ((LayoutGroup)item).ExpandOnDoubleClick = true;  
                }  
            }  
        }  


        protected override void OnActivated()  
        {  
            base.OnActivated();  
            View.ModelSaved += View_ModelSaved;  
            ((WinLayoutManager)(View.LayoutManager)).ItemCreated += ExpandableLayoutGroupViewControllercs_ItemCreated;  
        }  

        void ExpandableLayoutGroupViewControllercs_ItemCreated(object sender, ItemCreatedEventArgs e)  
        {  
            if (e.ModelLayoutElement is IModelLayoutGroup)  
            {  
                IModelLayoutGroup lg = e.ModelLayoutElement as IModelLayoutGroup;  
                if ((lg as IModelLayoutGroupExtender).Expandable)  
                    layoutGroups.Add(e.Item.Name, (IModelLayoutGroupExtender)e.ModelLayoutElement);  
            }  
        }  

        protected override void OnDeactivated()  
        {  
            ((WinLayoutManager)(View.LayoutManager)).ItemCreated -= ExpandableLayoutGroupViewControllercs_ItemCreated;  
            View.ModelSaved -= View_ModelSaved;  
            base.OnDeactivated();  
        }  

        void View_ModelSaved(object sender, EventArgs e)  
        {  
            foreach (BaseLayoutItem item in ((LayoutControl)View.Control).Items)  
            {  
                if (item is LayoutControlGroup && layoutGroups.ContainsKey(item.Name))  
                {  
                    layoutGroups[item.Name].Expanded = ((LayoutGroup)item).Expanded;  
                }  
            }  
        }  
    }  

JeyKey