private void AddToBackStack(
            IViewModel viewModel,
            FrameworkElement content)
        {
            var origin = new NavigationStackEntry(
                viewModel,
                content);

            BackStack.Add(origin);
        }
        private void SetCurrent(
            IViewModel viewModel,
            FrameworkElement content)
        {
            Current = new NavigationStackEntry(
                viewModel,
                content);


            RaisePropertyChanged(
                nameof(CanGoBack));

            RaisePropertyChanged(
                nameof(CanGoForward));
        }