public async Task RebuildOrder(OrderDetail orderDetail)
        {
            var L = Polozkas.Where(x => x.itemId == orderDetail.itemId).Select(x => x).FirstOrDefault();//připoj cenu

            orderDetail.Price    = L.price;
            orderDetail.ItemName = L.name;
            OrderDetails.Add(orderDetail);
            await Task.FromResult(true);
        }
        public async Task GetPolozkas()
        {
            if (IsBusy)
            {
                return;
            }
            IsBusy          = true;
            PolozkasService = new PolozkasService();
            Polozkas.Clear();
            var s = await PolozkasService.GetItemsAsync();

            foreach (var item in s)
            {
                Polozkas.Add(item);
            }

            IsBusy = false;
        }