public RegisterPageViewModel(
     INavigationService navigationService,
     IRegexHelper regexHelper,
     IApiService apiService,
     IFilesHelper filesHelper) : base(navigationService)
 {
     _navigationService = navigationService;
     _regexHelper       = regexHelper;
     _apiService        = apiService;
     _filesHelper       = filesHelper;
     Title     = Languages.Register;
     Image     = App.Current.Resources["UrlNoImage"].ToString();
     IsEnabled = true;
     User      = new UserRequest();
     Roles     = new ObservableCollection <Role>(CombosHelper.GetRoles());
     Campaigns = new ObservableCollection <Campaign>(CombosHelper.GetCampaigns());
 }