public override Fragment GetItem(int position)
        {
            switch (position)
            {
            case 0:
                return(ListFragment.NewInstance());

            case 1:
                return(CalculationsFragment.NewInstance());
            }

            return(null);
        }
        /**
         * Returns a new instance of this fragment for the given section
         * number.
         */
        public static ListFragment NewInstance()
        {
            var fragment = new ListFragment();

            return(fragment);
        }