async Task LoadContacts()
{
var watch = Stopwatch.StartNew();
IContactServices contactServices = (Application.Current as App).contactServices;
contactServices.OnContactLoaded += OnContactLoaded;
try { await contactServices.ContactsAsync(); }
catch (TaskCanceledException) { Console.WriteLine("Task was cancelled"); }
contactServices.OnContactLoaded -= OnContactLoaded;
watch.Stop();
var elapsedMs = watch.Elapsed.TotalSeconds;
Debug.WriteLine("Tiempo al leer los contactos: " + elapsedMs + " seg");
}