Question

Need help with this please.
I need to save some data in session to DB on controller action. But i get the “An entity object cannot be referenced by multiple instances of IEntityChangeTracker in C#” error on
answer.Add(answer);

can anybody help me with this?

Questionare questionare = unitOfWork.QuestionareRepository.GetByID(id);



            SADEntitiesContext db = new SADEntitiesContext();

            foreach (Question question in questionare.Questions)
            {
                //check if there are data in Session and save it
                _question = "question"+question.QuestionID.ToString();


                if (Session[_question] != null)
                {

                    var answer = new Answers();
                    if (TryUpdateModel(answer))
                    {

                    questionanswer = (QuestionAnswerData)Session[_question];
                    int qID = Int16.Parse(questionanswer.QuestionID);
                    var answertoupdate = answer.GetAnswer(qID, questionanswer.UserID, questionanswer.EmployeID);


                    //db.Answers.Remove(answertoupdate);


                    answer.UserName = questionanswer.UserID;
                    answer.Answer = db.AnswerChoices.Find(Int16.Parse(questionanswer.AnswerID));
                    answer.AnsweredAt = DateTime.Now;
                    answer.locked = false;
                    answer.Question = question;
                    answer.Questionare = questionare;
                    if (questionanswer.EmployeID != null)
                    {
                        answer.AnswerAboutUser = questionanswer.EmployeID;
                    }
                    if (answertoupdate != null)
                    {
                        answertoupdate = answer;

                        ok = (answertoupdate.Save() > 0);
                    }

                    else
                    {
                        answer.Add(answer);


                        ok = (answer.Save() > 0);
                    }
                    }
                }

answers class
public class Answers
{

    SADEntitiesContext db = new SADEntitiesContext();

    public int AnswersId { get; set; }

    //[Display(Name = "DataResposta", ResourceType = typeof(Resources))]
    public DateTime AnsweredAt { get; set; }

    //[Display(Name = "bloqueado", ResourceType = typeof(Resources))]
    public bool locked { get; set; }

   // [Display(Name = "UserName", ResourceType = typeof(Resources))]
    public string UserName { get; set; }

    //[Display(Name = "AnswersAboutUser", ResourceType = typeof(Resources))]
    public string AnswerAboutUser { get; set; } 

    //[Display(Name = "Resposta", ResourceType = typeof(Resources))]
    public virtual AnswerChoices Answer { get; set; } 

    //[Display(Name = "Questionare", ResourceType = typeof(Resources))]
    public virtual Questionare Questionare { get; set; }

    //[Display(Name = "QuestionID", ResourceType = typeof(Resources))]
    public virtual Question Question { get; set; }


    //
    // Persistence 

    public int Save()
    {
        return db.SaveChanges();
    }


    public Answers GetAnswer(int questionID, string employeID, string userID)
    {
        return db.Answers 
            .Where(e => e.UserName == userID
                                             && e.Question.QuestionID == questionID
                                             && e.AnswerAboutUser == employeID)

                                         .FirstOrDefault();

    }

    public Answers GetAnswer(int id)
    {
        return db.Answers.SingleOrDefault(d => d.AnswersId == id);
    }

    //
    // Insert/Delete Methods

    public void Add(Answers _answer)
    {
        db.Answers.Add(_answer);
        db.SaveChanges();
    }
}

}

Answer 1

Your problem is you’re calling an answer from one context:

answer.Answer = db.AnswerChoices.Find(Int16.Parse(questionanswer.AnswerID));

and then attempting to save it using a different in your Answer class:

  SADEntitiesContext db = new SADEntitiesContext();

The quickest solution to your problem would be to be able to set the context in your Answer class, so that your not jumping contexts, or you could Detach the answer after pulling it from the db the first time, and then reattach it in the save.

However, I think you have a more fundamental problem. Are you sure it’s a good idea to have a class be able to create it’s own context, and save itself? You’ll have problems like this all over the place.