public IEnumerable <Advertisment> GetAdvertisments(string expression, string userId = null)
{
// exclude user's adverts
if (!string.IsNullOrEmpty(userId))
{
return(_adverismentRepository.GetAdvertisments(userId, expression));
}
// include user's adverts'
return(_adverismentRepository.GetAdvertismentsIncludingUserOwn(expression));
}
