A second operation started on this context before a previous asynchronous operation completed

[AlexGeller]

Hi,

I need a function to update an entity, and then set the EventBus to do something in backgroud. the code is like this:

But I get the following error:

ERROR 2018-05-02 20:09:15,176 [7 ] lers.Filters.AbpExceptionFilterAttribute - System.NotSupportedException: A second operation started on this context before a previous asynchronous operation completed. Use 'await' to ensure that any asynchronous operations have completed before calling another method on this context. Any instance members are not guaranteed to be thread safe.
at System.Data.Entity.Internal.ThrowingMonitor.EnsureNotEntered()
at System.Data.Entity.Core.Objects.ObjectContext.SaveChangesAsync(SaveOptions options, CancellationToken cancellationToken)
at System.Data.Entity.Internal.InternalContext.SaveChangesAsync(CancellationToken cancellationToken)
at System.Data.Entity.Internal.LazyInternalContext.SaveChangesAsync(CancellationToken cancellationToken)
at Abp.EntityFramework.AbpDbContext.d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Abp.EntityFramework.Uow.EfUnitOfWork.d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Abp.EntityFramework.Uow.EfUnitOfWork.d__1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Abp.EntityFramework.Uow.EfUnitOfWork.d__6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Abp.Domain.Uow.UnitOfWorkBase.d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Abp.Domain.Uow.UnitOfWorkInterceptor.<>c__DisplayClass8.<b__2>d__d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Abp.Threading.InternalAsyncHelper.d__101.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Abp.Threading.InternalAsyncHelper.<AwaitTaskWithFinallyAndGetResult>d__c1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Threading.Tasks.TaskHelpersExtensions.d__3`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Controllers.ApiControllerActionInvoker.d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Controllers.ActionFilterResult.d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Controllers.AuthenticationFilterResult.d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Controllers.ExceptionFilterResult.d__0.MoveNext()

I think this is maybe HandleEvent function doesn't add await to the function it called. but it's error to add the await.

    public void HandleEvent(SendCampaignEventData eventData)
    {
        LogHelper.LogText("A task is completed by id = " + eventData.CampaignId);
        _seMailAppService.CreateTempTable(eventData.CampaignId);
    }

Can you tell me how to fix this?

Alex.

[acjh]

ABP v3.5 has IAsyncEventHandler.

[hikalkan]

If CreateTempTable is async, you must await it. You can either use IAsyncEventHandler as @acjh stated or use AsyncHelper.RunSync(() => _seMailAppService.CreateTempTable(eventData.CampaignId));

For doing something in background, you can use background jobs. Starting a thread without watching it and handling problems is not a good practice. Even if you do that, you should start a new unit of work (TransactionScopeOption.RequiresNew) to not use the same dbcontext with the calling code.

As you can see you have some options. Select the one you like :)