asp.net-mvc – 洋葱架构 – 服务层责任

我正在学习Jeffrey Palermo的Onion Architecture两周多了.我按照 this tutorial创建了一个测试项目.在学习期间,我遇到了关于SO的 this问题.根据接受的答案,一个人nwang建议像GetProductsByCategoryId这样的方法不应该在Repository中,另一方面不应该在Dennis Traub中
表明它是存储库的责任.我在做的是：

我在Domain.Interface中有一个通用存储库,其中我有一个方法查找：

public interface IRepository<TEntity> where TEntity : class
{
     IEnumerable<TEntity> Find(Expression<Func<TEntity,bool>> filter = null);
     .......
     .......
     .......
}

然后我在Infrastucture.Data中创建了一个BaseRepository：

public class RepositoryBase<TEntity> : IRepository<TEntity> where TEntity : class
{
     internal readonly DbSet<TEntity> dbSet;
     public virtual IEnumerable<TEntity> Find(
            Expression<Func<TEntity,bool>> filter = null)
     {
            IQueryable<TEntity> query = dbSet;

            if (filter != null)
            {
                query = query.Where(filter);
            }
            return query.ToList();
     }
}

我在Infrastructure.Data中有一个具体的存储库

public class ProductRepository : RepositoryBase<Product>,IProductRepository
{
      public ProductRepository(MyDBContext context)
           : base(context)
       {         

       }
}

现在,我在服务层中所做的是将存储库注入服务并调用Repository.Find以获取GetProductsByCategoryId等方法.喜欢 ：

public class ProductService : IProductService
{
     private readonly IUnitOfWork _unitOfWork;
     private readonly IProductRepository _productRepository;

     public ProductService(IUnitOfWork unitOfWork,IProductRepository productRepository)
     {
          _unitOfWork = unitOfWork;
          _productRepository = productRepository;
     }

     public IList<Product> GetProductsByCategoryId(int CategoryId)
     {
          // At the moment,My code is like this:
          return _productRepository.Find(e => e.CategoryId == CategoryId).ToList();

          // My confusion is here. Am I doing it right or I need to take this code to 
          // ProductRepository and call _productRepositoy.GetProductsByCategoryId(CategoryId) here instead.
          // If I do this,then Service Layer will become more of a wrapper around repository. Isn't it?
          // My question is : What exactly will be the responsibility of the Service Layer in Onion Architecture?
         }
    }

private readonly IProductRepository _productRepository;

private readonly IProductDescriptionService _productDescriptionService;