实体框架-导航属性是否不渴望/延迟加载？

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; }
}

当我在控制器中按以下方式创建新故障单时：

 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 ，尽管设置了RequestBy值，为什么为什么要加载相关的导航属性Priority而不是Requester导航属性？ 如您所见，我尚未针对任一导航属性定义任何virtual关键字？

扼杀这种情况仅适用于ApplicationUser类型的所有导航属性。 即使不使用virtual关键字，所有其他导航属性似乎也已加载？？？

我使用流利的api定义了RequestBy FK，如下所示：

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

以下是提供更多上下文的其他代码。

票库：

public class TicketRepository : ITicketRepository
{
    private readonly ApplicationDbContext _context;

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

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

优先级存储库：

public class PriorityRepository : IPriorityRepository
{
    private readonly ApplicationDbContext _context;

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

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

工作单位：

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

都不应该加载任何导航属性。 您看到的内容很可能是所谓的导航属性修复功能的结果-如果上下文已经跟踪了实体，即使您没有特别要求，EF也会更新引用该实体的实体的导航属性。

您可以使用var _context = new YourDbContext();轻松地进行验证var _context = new YourDbContext(); 局部变量而不是_context字段。 或类似这样的东西：

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应该为true而userLoaded - false 。