public async Task ClickLoginOnLoginPage()
        {
            // legitimize action
            if (ModalState != ModalState.Login)
            {
                throw new Exception("Can't ClickLogin if not on Login page");
            }

            ModalState = ModalState.Empty;
            ModalCount--;
            switch (NavState)
            {
            case NavState.OnMainPage:
                await ExpectedMainPage.OnAppearingAsync();

                break;

            case NavState.OnUomsPage:
                await ExpectedUomsCollectionPage.OnReappearingAsync();

                break;

            case NavState.OnUomItemPage:
                await ExpectedUomItemPage.OnAppearingAsync();

                break;

            case NavState.Empty:
                break;

            default:
                break;
            }
        }
        public async Task ClickBackOnUomsPage()
        {
            // legitimize action
            if (NavState != NavState.OnUomsPage)
            {
                throw new Exception("Can't ClickBackOnUomsPage() if not on Uoms page");
            }

            NavState = NavState.OnMainPage;
            await ExpectedMainPage.OnAppearingAsync();

            NavCount--;
        }