EF错误:在上一个异步操作完成之前,在此上下文上启动了第二个操作

我是Blazor的新手,在服务器端Blazor应用程序(.NET 5)中工作时有以下几点:

 <EditForm Model="@MyObject" OnValidSubmit="Submit">
      <DataAnnotationsValidator />
      <ValidationSummary />

     <InputText id="name" @bind-Value="MyObject.Name" />

     <button type="submit">Submit</button>
</EditForm>

代码隐藏:

public MyObject MyObject { get; set; } = new MyObject();
    
[Inject]
private IMyObjectService myObjectService { get; set; }

[Inject]
private NavigationManager navigationManager { get; set; }

void Submit()
{
    var created = myObjectService.CreateMyObject(MyObject);

    if (created != null)
    {
        navigationManager.NavigateTo("myobjects/manage");
    } else
    {
        // do something
    }
}

private readonly ApplicationDbContext _dbContext;

public MyObjectRepo(ApplicationDbContext dbContext)
{
   _dbContext = dbContext;
}

public async Task<MyObject> CreateMyObject(MyObject MyObject)
{
   _dbContext.Add(MyObject);
   await _dbContext.SaveChangesAsync();
   return MyObject;
}

public async Task<bool> DoesMyObjectExistByName(string name)
{
    var exists = await _dbContext.MyObjects.AnyAsync(x => x.Name == name);

    if (exists) return true;
    return false;
}

然后我有一个 MyObjectService :

private readonly IMyObjectRepo _myObjectRepo ;
        
public MyObjectService(IMyObjectRepo myObjectRepo  )
{
    _myObjectRepo  = myObjectRepo;
}

public async Task<MyObject> CreateMyObject(MyObject MyObject)
{
   if (MyObject == null) throw new ArgumentNullException("MyObject cannot be null.");

   // THIS LINE THROWS THE EF ERROR
   var exists = await _myObjectRepo.DoesMyObjectExistByName(MyObject.Name);

   if (!exists)
   {
      return await _myObjectRepo.CreateMyObject(MyObject);
   } else
   {
      return null;
   }
}

错误:System.InvalidOperationException异常:第二次操作失败 在上一个操作完成之前在此上下文上启动。这是 通常由不同线程同时使用同一个 DbContext的实例。

services.AddDbContext<ApplicationDbContext>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("Default")),
        ServiceLifetime.Transient);

services.AddAutoMapper(typeof(Startup));
services.AddScoped<IMyObjectRepo, MyObjectRepo>();
services.AddScoped<IMyObjectService, MyObjectService>();

我想我使用了所有正确的语法来保证异步/等待和线程安全,有什么想法吗?