public override void Start()
        {
            List <Triangle> triangles = _TrianglesRepo.GetTriangles();

            TriangleListItems = CreateListViewModelsFromTriangeList(triangles);
            SelectedTriangleListItemViewModel = TriangleListItems.FirstOrDefault();

            _TrianglesRepo.TriangleAdded += OnTriangleAdded;
        }
        public double ComputeTotalArea()
        {
            var triangles = _TrianglesRepo.GetTriangles();

            return(triangles.Sum(triangle => 0.5 * triangle.Base * triangle.Height));
        }