錯誤：無法訪問已處理的對象。 此錯誤的一個常見原因是處理從依賴注入解決的上下文

Question

我正在 dotnet core 2.2 上開發一個應用程序

自從兩天以來，我一直在受這個如此著名的問題的困擾。 我一次又一次地修改了以下鏈接，但這些似乎不起作用：

• 注入 DbContext 時無法訪問 ASP.NET Core 中已處理的對象
• 無法訪問已處置的對象。 此錯誤的一個常見原因是處理上下文
• https://thinkrethink.net/2017/12/22/cannot-access-a-disposed-object-in-asp-net-core-when-injecting-dbcontext/

但似乎沒有什么能解決問題。

public class UserAccountController : BaseController
{
    private readonly UserAccountBL _userAccountBL;

    public UserAccountController(IConfiguration configuration,
                      ILogger<UserAccountBL> logger, ApplicationDbContext db, UserManager<AppUser> accountManager)
    {
        _userAccountBL = new UserAccountBL(configuration,logger,db, accountManager);
    }

    [HttpPost("addnewUser")]
    public async Task<IActionResult> AddNewUser(UserVM user)
    {
        try
        {
            var result = _userAccountBL.AddUser(user);
            return Ok(result);
        }
        catch(NotFoundException e)
        {
            return Ok(new NotFoundError(e.Message));
        }
    }
}

public class DeliveryManagerAccountBL
{
    private readonly IConfiguration _configuration;
    private readonly ILogger<UserAccountBL> _logger;
    private readonly ApplicationDbContext _context;
    private readonly UserManager<AppUser>_accountManager;

    public UserAccountBL(IConfiguration configuration,
                      ILogger<UserAccountBL> logger, ApplicationDbContext db, UserManager<AppUser> accountManager)
    {
        _configuration  = configuration;
        _logger         = logger;
        _context        = db;
        _accountManager = accountManager;
    }

    public async Task<bool> AddUser( AddRiderVM user)
    {
        if (CheckEmailExist(model.EmailAddress))
        {
            throw new InvalidOperationException("Email already exist");
        }
        if (CheckPhoneExist(model.MobileNumber))
        {
            throw new InvalidOperationException("Mobile number already exist");
        }

        var newUserID = Guid.NewGuid().ToString();
        var user = new AspNetUser
        {
            UserName = user.EmailAddress,
            Email = user.EmailAddress,
            Id = newUserID,
            PhoneNumber = user.MobileNumber
        };

        var password = "Dumy123@";

        try
        {
            List<string> roles = new List<string>();

            **var result = await _accountManager.CreateAsync(user, password);**

            if (result.Succeeded)
            {
              //Something will happen
            }
        }
        catch(Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
        return false;
    }
}

以下異常發生在 ** 行。

無法訪問已處置的對象。 此錯誤的一個常見原因是處理從依賴注入解析的上下文，然后嘗試在應用程序的其他地方使用相同的上下文實例。 如果您在上下文上調用 Dispose() 或將上下文包裝在 using 語句中，則可能會發生這種情況。 如果你使用依賴注入，你應該讓依賴注入容器來處理上下文實例。 對象名稱：'ApplicationDbContext'。

以下是我的 Program.cs 文件

public class Program
{
    public static void Main(string[] args)
    {
       var host = CreateWebHostBuilder(args).Build();

        //seed database
        using (var scope = host.Services.CreateScope())
        {
            var services = scope.ServiceProvider;

            try
            {
                var databaseInitializer = services.GetRequiredService<IDatabaseInitializer>();
                databaseInitializer.SeedAsync().Wait();
            }
            catch (Exception ex)
            {
                var logger = services.GetRequiredService<ILogger<Program>>();
                logger.LogCritical(LoggingEvents.INIT_DATABASE, ex, LoggingEvents.INIT_DATABASE.Name);

                throw new Exception(LoggingEvents.INIT_DATABASE.Name, ex);
            }
        }
        host.Run();
    }

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .UseStartup<Startup>();
}

編輯：堆棧跟蹤：

at Microsoft.EntityFrameworkCore.DbContext.CheckDisposed()
   at Microsoft.EntityFrameworkCore.DbContext.get_DbContextDependencies()
   at Microsoft.EntityFrameworkCore.DbContext.<SaveChangesAsync>d__53.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Identity.EntityFrameworkCore.UserStore`9.<CreateAsync>d__22.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Microsoft.AspNetCore.Identity.UserManager`1.<CreateAsync>d__74.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Microsoft.AspNetCore.Identity.UserManager`1.<CreateAsync>d__79.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at StilaarApi.Core.AccountManager.<CreateUserAsync>d__10.MoveNext() in D:\project stilaar\pinchapi\Core\AccountManager.cs:line 106

Answer 1

我在調用函數 await _userAccountBL.AddUser(user); 時缺少 await 關鍵字；