c# - EF4.1 代码优先 DbContext : The operation cannot be completed because the DbContext has been disposed

Question

我有一个直接调用的 Controller 操作，但抛出了这个错误:

The operation cannot be completed because the DbContext has been disposed.

我只在网上找到了有关延迟执行的解决方案，但我认为这不适用于此处，因为我在任何地方使用上下文(在本例中)我都调用 .ToList() 或 .FirstOrDefault()。这是我的代码:

Controller 内容

    private IUnitOfWork UnitOfWork;
    public MyFavouritesController(
        IAccountServices accountServices,
        IUnitOfWork unitOfWork
        )
    {
        AccountServices = accountServices;
        UnitOfWork = unitOfWork;
    }

    public ActionResult Index()
    {
        int? id = AccountServices.GetCurrentUserId();
        if (!id.HasValue)
        {
            return RedirectToAction("Login", "Account", new { ReturnUrl = this.HttpContext.Request.Url.AbsolutePath });
        }
        var user = UnitOfWork.UserRepo.Get(id.Value, "Favourites", "Favourites.County", "Favourites.Country");
        //THE ABOVE CALL GETS THE ERROR

        //.....
        return View();
    }

存储库基类

public class RepositoryBase<C, T> : IDisposable
    where C:DbContext, new()
    where T : ModelBase
{
    private DbContext _context;
    public DbContext Context
    {
        get
        {
            if (_context == null)
            {
                _context = new C();
                this.AllowSerialization = true;
            }
            return _context;
        }
        set
        {
            _context = value;
        }
    }

    public virtual T Get(int Id, params string[] includes)
    {
        if (Id > 0)
        {
            var result = Context.Set<T>().Where(t => t.Id == Id);
            foreach (string includePath in includes)
            {
                result = result.Include(includePath);
            }
            return result.FirstOrDefault(); //This is where the error occurs.
        }
        else
        {
            throw new ApplicationException("Id is zero (0).");
        }
    }

    //... (More CRUD methods)

    public void Dispose()
    {
        if (Context != null)
        {
            Context.Dispose(); //Debugger never hits this before the error
        }
    }
}

工作类单元

public class UnitOfWork:IUnitOfWork
{
    public UnitOfWork(
        //... DI of all repos
        IUserRepository userRepo
        )
    {
        //... save repos to an local property
        UserRepo = userRepo;

        //create a new instance of the context so that all the repo's have access to the same DbContext
        Context = new Context();

        //assign the new context to all the repo's
        //...
        UserRepo.Context = Context;
    }

    public Context Context { get; set; }

    public IUserRepository UserRepo { get; set; }

    //... (some more repositories)

    public void Dispose()
    {
        Context.Dispose(); //THIS IS NOT HIT AT ALL
    }
}

最后，模型容器有这条线

_Instance.RegisterType<IUnitOfWork, UnitOfWork>(new PerThreadLifetimeManager());

如您所见，索引操作将接收一个新的 UnitOfWork 实例，其中包含一个新的 DbContext 对象。但是在第一次调用此上下文时，它会抛出上述错误。这种模式适用于我的代码中的任何其他地方。

谢谢

更新

下面的答案是使用 perRequestLifetimeManager。下面是 one in unity 的实现:

    public class HttpRequestLifetimeManager : LifetimeManager
    {
        private string _key = Guid.NewGuid().ToString();

        public override object GetValue()
        {
            if (HttpContext.Current != null && HttpContext.Current.Items.Contains(_key))
                return HttpContext.Current.Items[_key];
            else
                return null;
        }

        public override void RemoveValue()
        {
            if (HttpContext.Current != null)
                HttpContext.Current.Items.Remove(_key);
        }

        public override void SetValue(object newValue)
        {
            if (HttpContext.Current != null)
                HttpContext.Current.Items[_key] = newValue;
        }
    }

Answer 1

我注意到您正在使用 PerThreadLifetimeManager 来控制您的工作单元类的创建和处置。如果您的 IoC 容器支持，您可能应该将其更改为类似 PerRequestLifetimeManager 的内容。