Ошибка при выполнении GetAsync-метода

public List<Logistic.Model.Object> GetProviders()
{
    var context = new LogisticEntities();
    var list = context.Objects.Where(o => o.TypeObject.description.ToLower().Contains("provider")).ToList();
    return list;
}
public List<string> GetProviderNames()
{
    var context = new LogisticEntities();
    var list = context.Objects.Where(o => o.TypeObject.description.ToLower().Contains("provider")).Select(c => c.name).ToList();
    return list;
}

public TransportViewModel()
{
    LogisticServiceClient client = new LogisticServiceClient();
    client.GetProvidersCompleted += new EventHandler<GetProvidersCompletedEventArgs>(client_GetProvidersCompleted)
    client.GetProvidersAsync(); //здесь исключение
 
    client.GetProviderNamesCompleted += new EventHandler<GetProviderNamesCompletedEventArgs>(client_GetProviderNamesCompleted);
    client.GetProviderNamesAsync(); //но здесь все хорошо
}
 
private ObservableCollection<string> providerNames;
public ObservableCollection<string> ProviderNames
{
    get { return providerNames; }
    set
    {
        providerNames = value;
        RaisePropertyChanged("ProviderNames");
    }
}
 
private ObservableCollection<LogisticService.Object> providers;
public ObservableCollection<LogisticService.Object> Providers
{
    get { return providers; }
    set
    {
        providers = value;
        RaisePropertyChanged("Providers");
    }
}
 
void client_GetProvidersCompleted(object sender, GetProvidersCompletedEventArgs e)
{
    Providers = e.Result;
}
 
void client_GetProviderNamesCompleted(object sender, GetProviderNamesCompletedEventArgs e)
{
    ProviderNames = e.Result;
}
}