public HttpResponseMessage DeleteTodoList(int id)
        {
            TodoList todoList = db.TodoLists.Find(id);
            if (todoList == null)
            {
                return Request.CreateResponse(HttpStatusCode.NotFound);
            }

            if (db.Entry(todoList).Entity.UserId != User.Identity.Name)
            {
                // Trying to delete a record that does not belong to the user
                return Request.CreateResponse(HttpStatusCode.Unauthorized);
            }

            TodoListDto todoListDto = new TodoListDto(todoList);
            db.TodoLists.Remove(todoList);

            try
            {
                db.SaveChanges();
            }
            catch (DbUpdateConcurrencyException)
            {
                return Request.CreateResponse(HttpStatusCode.InternalServerError);
            }

            return Request.CreateResponse(HttpStatusCode.OK, todoListDto);
        }
        public HttpResponseMessage PostTodoList(TodoListDto todoListDto)
        {
            if (!ModelState.IsValid)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            todoListDto.UserId = User.Identity.Name;
            TodoList todoList = todoListDto.ToEntity();
            db.TodoLists.Add(todoList);
            db.SaveChanges();
            todoListDto.TodoListId = todoList.TodoListId;

            HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, todoListDto);
            response.Headers.Location = new Uri(Url.Link("DefaultApi", new { id = todoListDto.TodoListId }));
            return response;
        }
        public HttpResponseMessage PutTodoList(int id, TodoListDto todoListDto)
        {
            if (!ModelState.IsValid)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            if (id != todoListDto.TodoListId)
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }

            TodoList todoList = todoListDto.ToEntity();
            if (db.Entry(todoList).Entity.UserId != User.Identity.Name)
            {
                // Trying to modify a record that does not belong to the user
                return Request.CreateResponse(HttpStatusCode.Unauthorized);
            }

            db.Entry(todoList).State = EntityState.Modified;

            try
            {
                db.SaveChanges();
            }
            catch (DbUpdateConcurrencyException)
            {
                return Request.CreateResponse(HttpStatusCode.InternalServerError);
            }

            return Request.CreateResponse(HttpStatusCode.OK);
        }