Filters in DDD Repository

Question

There is Campaign Entity and for that, I have CampaignRepository which have this functions

1. public IList FindAll();
2. public Campaign FindByCampaignNumber(st

Answer 1

I would go with creating two Specifications: TopCampaignSpec and CampaingCreatedSpec.

var spec = CampaignCreatedSpec.ThisYear();
var campaigns = CampaignsRepository.FindSatisfying(spec);

CampaingCreatedSpec can also be replaced with more generic DateRange class if you need this functionality elsewhere:

var thisYear = DateRange.ThisYear();
var campaigns = CampaignsRepository.FindByDateRange(spec);

I also highly recommend staying away from 'generic' repositories and entities. Please read this

From DDD perspective it does not matter whether data access code is implemented as SQL/HQL/ICriteria or even web service call. This code belongs to repository implementation (data access layer). This is just a sample:

public IList FindByDateRange(CampaignCreatedSpec spec) {
    ICriteria c = _nhibernateSession.CreateCriteria(typeof(Campaign));
    c.Add(Restrictions.Between("_creationDate", spec.StartDate, spec.EndDate));
    return c.List();
}