public CarModelTreeSearchProvider(
            EkCarTypeEnum?carType,
            string modelId,
            Action onBackToRoot)
        {
            _onBackToRoot = onBackToRoot;

            RetryOnErrorCommand = new RelayCommand(
                nameof(RetryOnErrorCommand),
                parameter =>
            {
                // only modifications request fail is possible
                UpdateModifications();
            });
            string manufacturerId = null;

            if (!String.IsNullOrEmpty(modelId) && modelId != "0")
            {
                var model = EkSettingsHelper.GetModelAndNameByModelId(modelId);
                carType        = model.CarType;
                manufacturerId = model.ManufacturerId.ToString();
            }
            _carType = carType;
            InitModelTree(carType, manufacturerId, null);
        }