实体框架核心引发DBUpdateConcurrencyException

我正在研究.NET核心实体框架。我有两个班级类型的清单。一个用于更新,另一个用于新条目,添加新记录都工作正常,但这是由上下文实现的。[模型]。添加但更新是由上下文完成的。[模型]。更新引发异常更新我知道没有记录在本地运行时更新。

$exception  {Microsoft.EntityFrameworkCore.DbUpdateConcurrencyException: Database operation expected to affect 1 row(s) but actually affected 0 row(s). Data may have been modified or deleted since entities were loaded. 

代码

List<AnswerDataModel> surveyResponseListToCreate = new 
List<AnswerDataModel>();

    List<AnswerDataModel> surveyResponseListToUpdate = new 
   List<AnswerDataModel>();

     if (surveyResponseListToUpdate.Count > 0)
            {
                foreach (var answerObject in surveyResponseListToUpdate)
                {
                    Context.Answers.Update(answerObject);

                    if (answerObject.AnswerOptions.Count > 0)
                    {
                        foreach (var optItem in answerObject.AnswerOptions)
                        {
                            AnswerOptionDataModel answOpt = new AnswerOptionDataModel();
                            answOpt = optItem;
                            Context.AnswerOptions.Update(answOpt);
                        }
                    }
                }
            }

        var recordsAffected = Context.SaveChanges();

            if (!UsingExternalTransaction)
            {
                FinalizeTransaction(recordsAffected);
            }