public SpeakerController(Services.ISpeakersService speakersService)
 {
     _speakersService = speakersService;
 }
 public SpeakersViewModel(Services.ISpeakersService speakersService)
     : base()
 {
     _speakersService = speakersService;
 }
 public SpeakersViewModel(Services.ISpeakersService speakersService, INavigationService navigationService)
     : base()
 {
     _speakersService   = speakersService;
     _navigationService = navigationService;
 }