ObjectDisposedException 尝试实现 DDD 项目

Question

当我尝试将我的 orderList 作为 IQueryable 返回时，我收到以下错误：

“ObjectDisposedException：无法访问已释放的对象。此错误的常见原因是释放从依赖注入中解析的上下文，然后尝试在应用程序的其他地方使用相同的上下文实例。如果您正在调用，则可能会发生这种情况Dispose() 在上下文上，或者将上下文包装在 using 语句中。如果您使用依赖注入，则应该让依赖注入容器负责处理上下文实例。 对象名称：'KeplerContext'"

附言。如果我直接在控制器上使用 DbContext，一切正常。

一些帮助？提前致谢。

我的控制器类是：

public class OrderController : Controller
{
    public readonly IAppOrder _IAppOrder;
    public readonly UserManager<User> _userManager;

    // Ps.: Directly for the context works fine
    //private readonly KeplerContext _context;

    public OrderController(IAppOrder IAppOrder, UserManager<User> userManager) //, KeplerContext context)
    {
        _IAppOrder = IAppOrder;
        _userManager = userManager;

        // Ps.: Directly for the context works fine
        //_context = context;
    }

    public async Task<IActionResult> Index(string sortOrder, int? pageNumber)
    {
        var user = await _userManager.GetUserAsync(User);

        var orderList = _IAppOrder.OrderList(user);
            ^^^^

        if (!orderList.Any())
        {
            TempData["info"] = "no orders.";
        }
        else
        {
            var orderActive = await _IAppOrder.GetLastOrder(user);

            if (orderActive.IdOrderStatus <= 5)
            {
                return RedirectToAction(nameof(OrderController.Order), "Order", new { Area = "App", Id = orderActive.IdOrder });
            }
        }

        // paging
        ViewData["CurrentSort"] = sortOrder;
        ViewData["NumSort"] = String.IsNullOrEmpty(sortOrder) ? "num_asc" : "";

        switch (sortOrder)
        {
            case "num_asc":
                orderList = orderList.OrderBy(s => s.IdOrder);
                break;
            default:
                orderList = orderList.OrderByDescending(s => s.IdOrder);
                break;
        }
        int pageSize = 8;

        return View(await PagingHelper<Order>.CreateAsync(orderList.AsNoTracking(), pageNumber ?? 1, pageSize));
    }
}

我的应用程序类：（Ps。我正在使用 DDD，为了简化问题，我省略了其他类）：

    public IQueryable<Order> OrderList (User user)
    {
        return _IOrder.OrderList(user);
    }

我的存储库类：

public class RepositoryOrder : RepositoryGenerics<Order>, IDomOrder
{
    private readonly DbContextOptions<KeplerContext> _optionsBuilder;

    public RepositoryOrder()
    {
        _optionsBuilder = new DbContextOptions<KeplerContext>();
    }

    public IQueryable<Order> OrderList(User user)
    {
        using var db = new DbContext(_optionsBuilder);

        var result = db.Order
            .Include(p => p.IdOrderStatusNavigation)
            .Include(p => p.IdNavigation)
            .Where(u => u.Id == user.Id)
            .AsQueryable();
         
        return result;
               ^^^^^^ <<< Error happens here!!!
    }
}

我的存储库泛型类：

public class RepositoryGenerics<T> : IDomGeneric<T>, IDisposable where T : class
{
    private readonly DbContextOptions<KeplerContext> _OptionsBuilder;

    public RepositoryGenerics()
    {
        _OptionsBuilder = new DbContextOptions<KeplerContext>();
    }

    public async Task Add(T obj)
    {
        using var data = new KeplerContext(_OptionsBuilder);

        await data.Set<T>().AddAsync(obj);
        await data.SaveChangesAsync();
    }

    public async Task Delete(T obj)
    {
        using var data = new KeplerContext(_OptionsBuilder);

        data.Set<T>().Remove(obj);
        await data.SaveChangesAsync();
    }

    public async Task<T> GetEntityById(int Id)
    {
        using var data = new KeplerContext(_OptionsBuilder);

        return await data.Set<T>().FindAsync(Id);
    }

    public async Task<List<T>> List()
    {
        using var data = new KeplerContext(_OptionsBuilder);

        return await data.Set<T>().AsNoTracking().ToListAsync();
    }

    public async Task Update(T obj)
    {
        using var data = new KeplerContext(_OptionsBuilder);

        data.Set<T>().Update(obj);
        await data.SaveChangesAsync();
    }


    // https://docs.microsoft.com/pt-br/dotnet/standard/garbage-collection/implementing-dispose
    bool disposed = false;
    SafeHandle handle = new SafeFileHandle(IntPtr.Zero, true);

    // "Dispose Pattern" 
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (disposed)
            return;

        if (disposing)
        {
            handle.Dispose();
        }

        disposed = true;
    }
}

Startup.cs 中的依赖注入：

        // Repository
        services.AddSingleton(typeof(IDomGeneric<>), typeof(RepositoryGenerics<>));
        ...
        services.AddSingleton<IDomOrder, RepositoryOrder>();
        ...

        // Inteface da Application
        ...
        services.AddSingleton<IAppOrder, AppOrder>();
        ...

        // Service Domain
        ...
        services.AddSingleton<IServiceOrder, ServiceOrder>();
        ...

Answer 1

您的RepositoryOrder.OrderList 正在返回IQueryable，这意味着您没有在方法范围内执行查询。所以我相信你看到的是，当查询最终被执行时，DbContext 已经被释放了，因为它在你离开方法范围后就被释放了。

您可以致电 ToList 而不是 AsQueryable。