UrhoSharp - Add object on scene after Urhosurface created

Hey guys , when i add the following code in my CreateScene() method , it works well and the object is created on the scene.

addItem(box);

However when the scene is loaded and i try to add items aftewards , they do not show up

UrhoApp?.addItem(box);

In my Urho Application

public async Task addItem(string tpe)
        {

            Node modelNode2 = scene.CreateChild(tpe);
            modelNode2.Position = new Vector3(5.0f, 1.0f, 5.0f);

            modelNode2.SetScale(10.0f);

            var obj2 = modelNode2.CreateComponent<StaticModel>();
            obj2.Model = cache.GetModel("Models/Box.mdl");
            obj2.SetMaterial(cache.GetMaterial("Materials/Stone.xml"));
            obj2.CastShadows = true;
        }

If you add that inside the key event, inside the Update event or inside a component it will work.
I’m not sure it will work, if you do that on a different thread. Are you execute that on a different thread?