public MainWindow()
        {
            InitializeComponent();

            // Initialize Nebula
            var service = NbService.GetInstance();

            service.TenantId    = "";
            service.AppId       = "";
            service.AppKey      = "";
            service.EndpointUrl = "https://baas.example.com/api";

            _viewModel  = new TodoViewModel();
            DataContext = _viewModel;

            _viewModel.Reload();
        }