Question

There are many errors here in SO, but this scenario I think its different.

I had some code that was working fine, I update one entity, etc. But the problem is that it was being cached, when I disabled caching with AsNoTracking(), then it started to throw this exception;

What I do its the following:
1. In the page I get a EcoBonusRequest.
2. The user clicks a button and it modifies the currentstatus proeprty, and it addsa a list item to a collection of workflowhistories, (an associated collection of the ecobonusrequestobject).
3. I call the udpate method, setting state to modified, here it throwed the exception.

Here is my code>

EcoBonusRequestRepository.cs

public void UpdateEcoBonusRequest(EcoBonusRequest ecoBonusRequest)
            {
                _context.EcoBonusRequests.Attach(ecoBonusRequest);
                _context.Entry(ecoBonusRequest).State = EntityState.Modified;
            }

EcoBonusRequestBL

public void Update(EcoBonusRequest ecoBonusRequest)
        {
            DALFacade.UpdateEcoBonusRequest(ecoBonusRequest);
        }

EcoBonusRequest Page

public void ChangeStatus(EcoBonusRequest ecoBonusRequest, string stepname, string who, string choosenoption)
        {

            ecoBonusRequest.WorkflowHistories = new List<WorkflowHistory>
                                                   {
                                                       new WorkflowHistory()
                                                           {
                                                               Date = DateTime.Now,
                                                               What = choosenoption,
                                                               StepName = stepname,
                                                               Who = who
                                                           }
                                                   };

            ecoBonusRequest.CurrentStatus = _currentStepBlo.StepName;
            var ecoBonusRequestBL = new EcoBonusRequestBL();
            ecoBonusRequestBL.Update(ecoBonusRequest);
        }

This is how I get the object first: (I am not going to paste all code from all layers here)

protected override void OnInit(EventArgs e)
        {
            var requestBaseId = RequestBaseId;
            if (requestBaseId != null)
            {
                EcoBonusRequest request = GetDBRequest(requestBaseId.Value);

In the dal

public IQueryable<EcoBonusRequest> FindEcoBonusRequests(System.Linq.Expressions.Expression<Func<EcoBonusRequest, bool>> predicate)
            {
                return _context.EcoBonusRequests.AsNoTracking().Where(predicate);
            }

Answer 1

Yeah this is a fun one, the issue here comes from trying to re-attach an entity which is already attached to the context. This can come from a logic error or perhaps you are reusing your context without clearing the attached objects. There is a local collection on the database which you can use to see what items are currently attached to the context.

ctx.YourEntityCollection.Local