Repository Layer 为您提供了对数据访问的额外抽象级别.而不是写

Repository Layer gives you additional level of abstraction over data access. Instead of writing

var context = new DatabaseContext();
return CreateObjectQuery<Type>().Where(t => t.ID == param).First();

要从数据库中获取单个项目，请使用存储库接口

to get a single item from database, you use repository interface

public interface IRepository<T>
{
    IQueryable<T> List();
    bool Create(T item);
    bool Delete(int id);
    T Get(int id);
    bool SaveChanges();
}

并调用Get(id).存储库层公开基本的CRUD 操作.

and call Get(id). Repository layer exposes basic CRUD operations.

服务层暴露业务逻辑，使用存储库.示例服务可能如下所示:

Service layer exposes business logic, which uses repository. Example service could look like:

public interface IUserService
{
    User GetByUserName(string userName);
    string GetUserNameByEmail(string email);
    bool EditBasicUserData(User user);
    User GetUserByID(int id);
    bool DeleteUser(int id);
    IQueryable<User> ListUsers();
    bool ChangePassword(string userName, string newPassword);
    bool SendPasswordReminder(string userName);
    bool RegisterNewUser(RegisterNewUserModel model);
}

虽然repository的List()方法返回所有用户，但IUserService的ListUsers()只能返回一个，用户可以访问.

While List() method of repository returns all users, ListUsers() of IUserService could return only ones, user has access to.

在 ASP.NET MVC + EF + SQL SERVER 中，我有这样的通信流程:

In ASP.NET MVC + EF + SQL SERVER, I have this flow of communication:

视图 <- 控制器 -> 服务层 -> 存储库层 -> EF -> SQL Server

Service layer -> Repository layer -> EF 这部分对模型进行操作.

Service layer -> Repository layer -> EF This part operates on models.

Views <- Controllers -> Service layer 这部分操作在视图模型上.

Views <- Controllers -> Service layer This part operates on view models.

/Orders/ByClient/5 的流程示例(我们希望查看特定客户的订单):

Example of flow for /Orders/ByClient/5 (we want to see order for specific client):

public class OrderController
{
    private IOrderService _orderService;

    public OrderController(IOrderService orderService)
    {
        _orderService = orderService; // injected by IOC container
    }

    public ActionResult ByClient(int id)
    {
        var model = _orderService.GetByClient(id);
        return View(model); 
    }
}

这是订单服务的接口:

public interface IOrderService
{
    OrdersByClientViewModel GetByClient(int id);
}

该接口返回视图模型:

public class OrdersByClientViewModel
{
     CientViewModel Client { get; set; } //instead of ClientView, in simple project EF Client class could be used
     IEnumerable<OrderViewModel> Orders { get; set; }
}

这是接口实现.它使用模型类和存储库来创建视图模型:

This is interface implementation. It uses model classes and repository to create view model:

public class OrderService : IOrderService
{
     IRepository<Client> _clientRepository;
     public OrderService(IRepository<Client> clientRepository)
     {
         _clientRepository = clientRepository; //injected
     }

     public OrdersByClientViewModel GetByClient(int id)
     {
         return _clientRepository.Get(id).Select(c => 
             new OrdersByClientViewModel 
             {
                 Cient = new ClientViewModel { ...init with values from c...}
                 Orders = c.Orders.Select(o => new OrderViewModel { ...init with values from o...}     
             }
         );
     }
}