Hi all,

this is my first post on Umbraco Community. I'm migrating the site code from v7 to v8 and I have a problem on method CancelOperation that should throw a bubble message on a new node save event (in the v7 code it works perfectly), in backoffice. That I notice is the code below works well when I save an existing node but it fails (simply the message is not showed) when i try to create a new node.

public class ValidateTagsComposer : IUserComposer
    {
        public void Compose(Composition composition)
        {
            composition.Components().Append<ValidateTagsComponent>();
        }
    }

    public class ValidateTagsComponent : IComponent
    {
        // initialize: runs once when Umbraco starts
        public void Initialize()
        {
            ContentService.Saving += ContentService_Saving;
        }

        // terminate: runs once when Umbraco stops
        public void Terminate()
        { }


        private void ContentService_Saving(IContentService sender, ContentSavingEventArgs eventArgs)
        {


            foreach (var node in eventArgs.SavedEntities)
            {
                if (node.HasProperty("govitCategory") && node.GetValue("govitCategory") != null)
                {
                    if (node.GetValue("govitCategory").ToString().Split(',').Length > 1)
                    {                        

                        // Explain why the publish event is cancelled
                        eventArgs.CancelOperation(new EventMessage("Categoria", "E' consentita una sola categoria.", messageType: EventMessageType.Error));

                    }
                }
            }
        }
    }

I already tried to use the other form suggested here in the forum, first setting eventArgs.Cancel = true; and then using the Add method eventArgs.Messages.Add(new EventMessage("Categoria", "E' consentita una sola categoria.", EventMessageType.Error));, but unfortunately it doesn't work: it is displayed only the following message:

'' could not be published, a 3rd party add-in cancelled the action.

Any ideas? Is it a possible bug?

Antonio