如何在实体框架模型中引用用户对象?

问题描述：

我有以下模型:

public class MyEntity
{
    public Guid Id { get; set; }
    public virtual ICollection<ApplicationUser> AssociatedUsers { get; set; }

    public MyEntity()
    {
        AssociatedUsers = new HashSet<ApplicationUser>();
    }
}

请注意，每个实体都有一些关联的用户.在我的控制器中，我试图像这样将 MyEntity 的实例添加到数据库中:

Notice that each entity has some associated users. In my controller, I'm trying to add an instance of MyEntity to the database like this:

private ApplicationDbContext db = new ApplicationDbContext();

// ...

ApplicationUser currentUser = System.Web.HttpContext.Current.GetOwinContext().GetUserManager<ApplicationUserManager>().FindById(System.Web.HttpContext.Current.User.Identity.GetUserId());

MyEntity entityInstance = new MyEntity();
entityInstance.Id = Guid.NewGuid();
entityInstance.AssociatedUsers.Add(currentUser);
db.MyEntities.Add(entityInstance);
db.SaveChanges();

但是，该代码引发以下错误:

However, that code throws the following error:

IEntityChangeTracker的多个实例不能引用一个实体对象.

An entity object cannot be referenced by multiple instances of IEntityChangeTracker.

我从该错误消息中收集到 CurrentUser 仍由数据库上下文管理，该上下文支持 ApplicationUserManager ，因此无法将其添加到其他上下文中.但与我发现的其他案例不同，href ="https://stackoverflow.com/questions/10191734/entity-object-cannot-be-referenced by-multiple-instances-of-ientitychangetracker">>，我不能简单地切换上下文以便它们共享数据库连接:用户对象来自 ApplicationUserManager .我需要怎么做才能解决这个问题?我是从根本上做错了吗?我知道我可以改用ID并查找相应的用户，但我希望直接访问该对象.

I gather from that error message that CurrentUser is still being managed by the database context which backs the ApplicationUserManager, so I can't add it to a different context. But unlike other cases that I have found documented, I can't simply switch the context so that they share a database connection: the user object is coming from an ApplicationUserManager. What do I need to do to resolve this? Am I doing something fundamentally wrong? I am aware that I could use the ID instead and look up the corresponding user, but I would rather have the object accessible directly.

答

您的问题与您发布的链接中的问题非常相似.简而言之，您无法在不同的上下文中操纵用户.在这里:

Your problem is very similar to the problem found in the link you've posted. In a few words, you can't manipulate a user from different contexts. Here:

ApplicationUser currentUser = System.Web.HttpContext.Current.GetOwinContext().GetUserManager<ApplicationUserManager>().FindById(System.Web.HttpContext.Current.User.Identity.GetUserId());

您实际上是从 System.Web.HttpContext.Current.GetOwinContext()中获取了 currentUser ，但是随后您尝试使用 db code>，它是 ApplicationDbContext .

You effectively got currentUser from System.Web.HttpContext.Current.GetOwinContext(), but then you're trying to save it using db, which is an ApplicationDbContext.

将其保留在相同的上下文中，您将可以解决问题:

Keep it on the same context, and you will have your problem solved:

var currentUser = db.Users.Find(System.Web.HttpContext.Current.User.Identity.GetUserId());

var entityInstance = new MyEntity();

entityInstance.Id = Guid.NewGuid();

entityInstance.AssociatedUsers.Add(currentUser);
db.MyEntities.Add(entityInstance);
db.SaveChanges();

如何在实体框架模型中引用用户对象?

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