ExampleQueries.cs

List<int> userIds = (from item in _userRepository.Fetch()
                                                 where item.Name.Contains(search)
                                                       || item.Role.Name.Contains(search)
                                                 select item.User.Id);

// Or 

var stuff = _repository.Fetch();
var result = stuff.Where(x => x.StuffId== someId && (x.StuffName == null || x.StuffType != null));

IQueryableRepository.cs

    public interface IQueryableRepository<T>: IRepository<T>
    {
        IQueryable<T> Fetch();
    }

QueryableRepository.cs

    public class QueryableRepository<T> : Repository<T>, IQueryableRepository<T>
    {
        // Repository<T> comes from Sharp Arch.
        public IQueryable<T> Fetch()
        {
            ISession session = Session;
            var query = from item in session.Linq<T>() select item;
            return query;
        }

    }