轨道交通。无法访问已处置的对象。对象名称：'MySqlConnection'

Question

项目实施过程中出现问题。任务是捕捉事件并在数据库中做一些工作。看起来一切都很简单，但我得到一个错误 “无法访问已释放的对象。对象名称：'MySqlConnection'。”我认为这个错误是由于 dbContext 并不真正存在。而且我不明白如何通过MassTransit转发它。

启动：

public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
        services.AddDbContext<AuthDbContext>(options => options.UseMySql(Configuration.GetConnectionString("IdentityServerConnection")));

        services.AddIdentity<ApplicationUserDTO, IdentityRole>();
        new IdentityBuilder(typeof(ApplicationUserDTO), typeof(IdentityRole), services)
        .AddEntityFrameworkStores<AuthDbContext>()
        .AddDefaultTokenProviders();

        //AutoMapper
        services.AddAutoMapper(typeof(MappingProfile));


        #region MassTransit RabbitMq

        services.AddScoped<CreateUserConsumer>();
        services.AddMassTransit(c =>
        {
            c.AddConsumer<CreateUserConsumer>();
        });
                  

       services.AddSingleton(provider => Bus.Factory.CreateUsingRabbitMq(conf =>
       {

           conf.Host(Configuration["Rabbit:Host"], host =>
           {
               host.Username(Configuration["Rabbit:Username"]);
               host.Password(Configuration["Rabbit:Password"]);
           });             

           conf.ReceiveEndpoint(Configuration["Rabbit:ReceiveEndpoint"], e =>
           {
               e.PrefetchCount = 16;
               e.UseMessageRetry(n => n.Interval(3, 100));

               #region                  
               e.Consumer<CreateUserConsumer>(provider);                  
               #endregion

           });             

       }));

        services.AddSingleton<IPublishEndpoint>(provider => provider.GetRequiredService<IBusControl>());
        services.AddSingleton<ISendEndpointProvider>(provider => provider.GetRequiredService<IBusControl>());
        services.AddSingleton<IBus>(provider => provider.GetRequiredService<IBusControl>());

        services.AddScoped(provider => provider.GetRequiredService<IBus>().CreateRequestClient<CreateUserConsumer>());

        services.AddSingleton<IHostedService, BusService>();

        #endregion


        #region Services 
        services.AddScoped<IAuth, AuthService>();
        #endregion
    }

消费者：

public class CreateUserConsumer : IConsumer<IUserCreate>
{
    private IAuth _authService;
    private IMapper _mapper;      
    public CreateUserConsumer(IAuth _authService, IMapper _mapper)
    {
        this._authService = _authService;
        this._mapper = _mapper;
        _context = context;
    }

    public Task Consume(ConsumeContext<IUserCreate> context)
    {
        var model = _mapper.Map<IUserCreate, UserRegisterDTO>(context.Message);                      
        var s = _authService.RegisterAsync(model);
        return Task.CompletedTask;
    }
}

AuthService:

public class AuthService : IAuth
    {
        private  UserManager<ApplicationUserDTO> _userManager;
        private  RoleManager<IdentityRole> _roleManager;
        private  IMapper mapper;

        public AuthService(
            UserManager<ApplicationUserDTO> userManager, 
            RoleManager<IdentityRole> roleManager,          
            IMapper mapper)
        {
            _userManager = userManager;
            _roleManager = roleManager;
            this.mapper = mapper;
        }

        public string Register(UserRegisterDTO model)
        {
            try
            {
                var newUser = _userManager.FindByNameAsync(model.UserName); //**Exception**
                if (newUser != null)
                {
                    throw new Exception("blablabla");
                }
            }
            catch (Exception exp)
            {
                var s = exp;
            }
            return "";           
        }
}

错误：

 fail: Microsoft.EntityFrameworkCore.Database.Command[20102]
       Failed executing DbCommand (121ms) [Parameters=[@__normalizedUserName_0='?' (Size = 256)],
 CommandType='Text', CommandTimeout='1200']
       SELECT `a`.`Id`, `a`.`AccessFailedCount`, `a`.`ConcurrencyStamp`, `a`.`Email`, `a`.`EmailConfirmed`, `a`.`FIO`,
 `a`.`LockoutEnabled`, `a`.`LockoutEnd`, `a`.`NormalizedEmail`,
 `a`.`NormalizedUserName`, `a`.`PasswordHash`, `a`.`PhoneNumber`,
 `a`.`PhoneNumberConfirmed`, `a`.`SecurityStamp`,
 `a`.`TwoFactorEnabled`, `a`.`UserName`
       FROM `AspNetUsers` AS `a`
       WHERE `a`.`NormalizedUserName` = @__normalizedUserName_0
       LIMIT 1 fail: Microsoft.EntityFrameworkCore.Query[10100]
       An exception occurred while iterating over the results of a query for context type 'Auth.API.Context.AuthDbContext'.
       System.ObjectDisposedException: Cannot access a disposed object.
       Object name: 'MySqlConnection'.
          at MySql.Data.MySqlClient.MySqlConnection.VerifyNotDisposed() in
 C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlConnection.cs:line
 707

我认为错误是由于当调用_UserManager 时，数据库上下文不再存在。

告诉我我做错了什么？！？！

Answer 1

我认为这是问题所在：

    var s = _authService.RegisterAsync(model);
    return Task.CompletedTask;

我相信甚至你的 IDE 也会发出警告“访问已处置的闭包”，因为你既没有等待任务也没有返回它。

这很可能会奏效

return _authService.RegisterAsync(model);

问题可能出在其他地方，因为我没有看到注册 DbContext 的代码。

此外，我建议按原样注册 MassTransit 和所有必需的依赖项 described in the docs。

轨道交通。无法访问已处置的对象。对象名称：'MySqlConnection'

Masstransit. Cannot access a disposed object. Object name: 'MySqlConnection'

mysql

identity

masstransit

dbcontext

.net-core