public MainPageViewModel(IClientDataService clientDataService,
                                 INavigationService navigationService)
        {
            _clientDataService = clientDataService ?? throw new ArgumentNullException(nameof(clientDataService));
            _navigationService = navigationService ?? throw new ArgumentNullException(nameof(navigationService));
            Title     = "Clients";
            BeginText = "Dit is een test text";
            Clients   = _clientDataService.GetClients(Config.Username);

            NavigateClientCommand = new Command <Client>(async(client) => await NavigateToClient(client));
        }