如何修复EntityFramework.dll中发生此异常类型'System.InvalidOperationException'但未在

Question

这是我的问题的延续：[How to get name data of multiple json object list that will be posted to web api?

我能够更新我的代码，但现在我在

上得到了一个erexception

if (db.Sales1.Any(sl => sl.ExtSerial != s.ExtSerial))

异常：EntityFramework.dll中发生了'System.InvalidOperationException'类型的异常，但未在用户代码中处理

附加信息：创建模型时无法使用上下文。如果在OnModelCreating方法中使用上下文，或者同时由多个线程访问相同的上下文实例，则可能抛出此异常。请注意，DbContext和相关类的实例成员不保证是线程安全的。

以下是代码：

public HttpResponseMessage PostSales(List<Sales> Sales, [FromUri] string auth)
        {
            try
            {
                if (ModelState.IsValid)
                {
                    if (auth == "KDI")
                    {
                        #region Stable but not multiline
                        //Int64 rs = db.Sales1.Where(sl => sl.Serial == Sales.Serial).Count();
                        //if (1 == rs)
                        //{
                        //    return Request.CreateErrorResponse(HttpStatusCode.Conflict, " Duplicate Found!");
                        //}
                        //else
                        //{
                        //    db.Sales1.Add(Sales);
                        //    db.SaveChanges();
                        //    return Request.CreateErrorResponse(HttpStatusCode.OK, "Added!");
                        //} 
                        #endregion
                        Parallel.ForEach(Sales, s =>
                        {
                            if (db.Sales1.Any(sl => sl.ExtSerial != s.ExtSerial))
                            {
                                db.Sales1.Add(s);
                                db.SaveChanges();
                            }
                            else
                            {
                                return;
                            }
                        });
                        return Request.CreateErrorResponse(HttpStatusCode.OK, "Success!");
                    }
                    else
                    {
                        return Request.CreateResponse(HttpStatusCode.Unauthorized, "Unauthorized Access!");
                    }
                }
                else
                {
                    return Request.CreateResponse(HttpStatusCode.InternalServerError, "Something's wrong with the JSON model you sent me.");
                }
            }
            catch (Exception ex)
            {
                return Request.CreateResponse(HttpStatusCode.InternalServerError, ex.Message);
            }

        }