How to propagate the notification for a collection of item that implements INotifyPropetyChanged?

[Snailya]

I have a class that implements INotifyPropertyChange. Then i need a correct type of collection to holds these class items.
Whenver the property of the item changed, I need to build the collection into a tree structure.
Before, i used to use SourceCache and update the source cache in a service using AddOrUpdate. But now I want the item to handle its update by itself, not a service.

[JakenVeina]

Whenver the property of the item changed, I need to build the collection into a tree structure.

Not really sure what you mean by this. Are you saying you want to derive a tree structure, based on properties of the items? Like each item has its ParentId as a notifying property?

[Snailya]

I'm creating an addin for visio which displays the shapes in the page as a tree structure.
To make the tree item properties updates synchronously with the shape, i maked the shape model in my code subscribe to the event in visio.
When initializing my tree, I firstly created a ObservableCollection.
Then convet it to a sourcecache of ShpeViewModel, which is just a property copy with no event subscrption.
Then to a tree structure using TransformToTree().
It readlly strange that, if i change the property of a shape which is not the root item, it works fun. But if i change the property of a root shape, it fails to reflect the change on UI and sub shape stop works etiher.
I don't know how to find out the bug, so I create a small WPF app, it works well.
Here is my code, maybe i'm doing the wrong way.
ShapeModel.cs

public abstract class ShapeModel: ReactiveObject, IDisposable {
    private readonly CompositeDisposable _cleanUp = new();
    protected readonly Visio.Shape Source;
    private int _parentId;
    private string _description = string.Empty;

   protected ShapeModel(Visio.Shape source)
    {
        Source = shape;
        Id = shape.ID;

        Observable
            .FromEvent<EShape_CellChangedEventHandler, Cell>(
                handler => Source.CellChanged += handler,
                handler => Source.CellChanged -= handler)
            .Subscribe(OnCellChanged)
            .DisposeWith(_cleanUp);

        // observable on relationship change
        Observable
            .FromEvent<EShape_FormulaChangedEventHandler, Cell>(
                handler => Source.FormulaChanged += handler,
                handler => Source.FormulaChanged -= handler)
            .Where(cell => cell.Name == "Relationships")
            .Subscribe(_ => { OnRelationshipsChanged(); })
            .DisposeWith(_cleanUp);
    }

    public int Id { get; }
    public int ParentId
    {
        get => _parentId;
        protected set => this.RaiseAndSetIfChanged(ref _parentId, value);
    }
    public string Description
    {
        get => _description;
        protected set => this.RaiseAndSetIfChanged(ref _description, value);
    }
}

ShapeViewModel.cs is a reduced version of ShapeModel.cs without the Subscription.
In my PageViewModel

        var sourceCache = new SourceCache<ShapeViewModel, int>(t => t.Id);
        service.Elements
            .ToObservableChangeSet(t => t.Id)
            .AutoRefresh()
            .ObserveOn(RxApp.MainThreadScheduler)
            .Subscribe(changes =>
            {
                sourceCache.Edit(updater =>
                {
                    foreach (var change in changes)
                        switch (change.Reason)
                        {
                            case ChangeReason.Remove:
                                updater.Remove(change.Current.Id);
                                break;
                            case ChangeReason.Add:
                            case ChangeReason.Update:
                            case ChangeReason.Refresh:
                            case ChangeReason.Moved:
                            default:
                                var item = new ShapeViewModel(change.Current);
                                updater.AddOrUpdate(item);
                                break;
                        }
                });
            })
            .DisposeWith(d);

        sourceCache
            .Connect()
            .TransformToTree(x => x.ParentId)
            .Transform(node => new BOMTreeItemViewModel(node))
            .ObserveOn(RxApp.MainThreadScheduler)
            .Bind(out _bomTree)
            .DisposeMany()
            .Subscribe()
            .DisposeWith(d);

[JakenVeina]

I'm not familiar with the details of how the tree transforms work, myself, but everything you've described laid out sounds and looks correct, logically, I don't think you're missing anything fundamental about proper usage of DD.

What I'm failing to see here is the connection between ShapeModel and ShapeViewModel. Or are you saying that ShapeViewModel is from your smaller demo app, and that version works, but it's not working with ShapeModel in the full app? I'd also want to see what BOMTreeItemViewModel has in it.

If it were me, my next step would be to toss .Do(x => {}) into the stream, both before .TransformToTree() and after .Transform() and set breakpoints in them, in order to inspect exactly what changes are being published when you do whatever action it is that triggers a change to a root item. I would think you should see a Replace change in both cases .TransformToTree(). If you get nothing, the problem has gotta be upstream from where you populate sourceCache. If you see the first Replace but not the second one, either BOMTreeItemViewModel is somehow swallowing the changes, or there may be a bug within .TransformToTree() or .Transform(). If you see both Replace changes, start looking at your View layer, it may be that your {Binding}s are incorrect there, in some way that affects only root items.

[Snailya]

Thank you. Having struggle with it for hours, I think there is a high probability that something wrong with my custom control template.

[JakenVeina]

Happy to take a look at it.