Abstracted Async model in Silverlight 4.0

DataCache.cs

public IEnumerable<IResult> LoadLookupCache()
{
    yield return ProgressResult.Show("Loading Cache...");

    var masterDataService = new MasterDataServiceClient();
    var therapyService = new TherapyServiceClient();

    masterDataService.getAllHealthFundsCompleted += (o, e) => _serviceHandler.AddTo(e, _lookups.HealthFunds);
    masterDataService.getAllPatientCompleted += (o, e) => _serviceHandler.AddTo(e, _lookups.Patients);
    therapyService.getTherapyTypesCompleted += (o, e) => _serviceHandler.AddTo(e, _lookups.TherapyTemplateTypes).Apply(x => x.Type = TemplateTypes.Therapy);

    yield return new ServiceResult(masterDataService.getAllHealthFundsAsync);

    yield return new ServiceResult(masterDataService.getAllPatientAsync);

    yield return new ServiceResult(therapyService.getTherapyTypesAsync);

    yield return ProgressResult.Hide();
}