Entity Framework - 导航属性未 Eager/Lazy 加载？

Question

我有以下实体：

public class Ticket 
{
    public int Id { get; set; }
    public string RequestBy { get; set; }
    public int PriorityId { get; set; }

    public ApplicationUser Requester { get; set; }
    public Priority Priority { get; set; }
}

public class ApplicationUser
{
    public ApplicationUser()
    {
        Id = Guid.NewGuid().ToString();
    }

    public string FirstName { get; set; }
    public string LastName { get; set; }
}

public class Priority
{
    public int Id { get; set; }
    public string Name { get; set; }
}

当我在我的控制器中创建一个新的 Ticket 时：

 public class BaseController : Controller
{
    protected readonly IUnitOfWork UnitOfWork;

    public BaseController(IUnitOfWork unitOfWork)
    {
        UnitOfWork = unitOfWork; 
    }
}

public class TicketController : BaseController
{
    public TicketController(IUnitOfWork unitOfWork) : base(unitOfWork) { }

    [HttpPost]
    public ActionResult CreateTicket(CreateTicketVM viewModel)
    {
         // repopulate dropdowns incase we need to return view
         // viewModel.Priorities is IEnumerable list
         viewModel.Priorities = UnitOfWork.PriorityRepository.GetPriorities();

        //validation code removed for brevity...

        var ticket = new Ticket
        {
           RequestBy = !string.IsNullOrEmpty(viewModel.RequestBy) ? viewModel.RequestBy : User.Identity.GetUserId(),
           PriorityId = viewModel.PriorityId != 0 ? viewModel.PriorityId : (int)PriorityLevel.Medium,
        };

        UnitOfWork.TicketRepository.Add(ticket);
    }
}

现在，当我在调用 .Add(ticket) 后调试 var ticket 时，为什么它加载了相关导航属性 Priority 而不是 Requester 导航属性尽管设置了 RequestBy 值？如您所见，我还没有针对任一导航属性定义任何 virtual 关键字？

Strangley 这只发生在 ApplicationUser 类型的所有导航属性中。即使不使用 virtual 关键字，所有其他导航属性似乎也会加载？？？

使用流利的 api 我定义了 RequestBy FK 如下：

modelBuilder.Entity<Ticket>()
 .HasRequired(x => x.Requester)
 .WithMany()
 .HasForeignKey(x => x.RequestBy);

下面是提供更多上下文的附加代码。

票证存储库：

public class TicketRepository : ITicketRepository
{
    private readonly ApplicationDbContext _context;

    public TicketRepository(ApplicationDbContext context)
    {
        _context = context;
    }

    public void Add(Ticket ticket)
    {
        _context.Ticket.Add(ticket);
    }
}

优先存储库：

public class PriorityRepository : IPriorityRepository
{
    private readonly ApplicationDbContext _context;

    public PriorityRepository(ApplicationDbContext context)
    {
        _context = context;
    }

    public IEnumerable<Priority> GetPriorities()
    {
        return _context.Priority.ToList();
    }
}

工作单元：

public class UnitOfWork : IUnitOfWork
{
    private readonly ApplicationDbContext _context;

    public ITicketRepository TicketRepository { get; private set; }
    public IPriorityRepository PriorityRepository { get; private set; }

    public UnitOfWork(ApplicationDbContext context)
    {
        _context = context;
        TicketRepository = new TicketRepository(_context);
        PriorityRepository = new PriorityRepository(_context);
    }

    public void Complete()
    {
        _context.SaveChanges();
    }
}

Answer 1

两个导航属性都不应加载。您看到的很可能是所谓的导航属性修复功能的结果 - 如果实体已被上下文跟踪，EF 会更新引用它的实体的导航属性，即使您没有特别要求。

您可以使用 var _context = new YourDbContext(); 局部变量而不是 _context 字段轻松验证这一点。或者像这样：

var ticket = new Ticket
{
    RequestBy = !string.IsNullOrEmpty(viewModel.RequestBy) ? viewModel.RequestBy : User.Identity.GetUserId(),
    PriorityId = viewModel.PriorityId != 0 ? viewModel.PriorityId : (int)PriorityLevel.Medium,
};

bool priorityLoaded = _context.Priority.Local.Any(e => e.Id == ticket.PriorityId);
bool userLoaded = _context.ApplicationUser.Local.Any(e => e.Id == ticket.RequestBy);

_context.Ticket.Add(ticket);

根据您的描述，priorityLoaded 应该是 true 而 userLoaded - false.

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