public void OnStart()
 {
     ShowCountryProgress = true;
     if (ContactEntity.IsNullOrEmpty())
     {
         ContactEntity = new ContactEntity();
     }
     //fetch countries for now
     countryCancelation = endpointClient.queryCountries()
                          .ToResponse <List <CountryEntity> >()
                          .SubscribeOn(ThreadPoolScheduler.Instance)
                          .ObserveOnDispatcher(DispatcherPriority.Background)
                          .Subscribe(OnSuccessCountries, OnErrorCountries, () => {
         ShowCountryProgress = false;
     });
 }