Entity Framework 4.0 如何更新对象
我要在方法里传入一个对象，用这个对象去更新数据库里的对角。
代码如下:
 public int UpdateNewsDoc(NewsDoc nd, EntityCollection<NewDocAttachments> Attachments, EntityCollection<InNewsPicSwf> InNewsPicSwfs)
        {
            try
            {
                using (var db = new JiXiaoWebSite_DAXLJWEntities())
                {
                    if (Attachments != null && Attachments.Count > 0)
                    {
                        IList<NewDocAttachments> DelAttachmentsList = Attachments.Where(a => a.IsDel == true).ToList();
                        while (DelAttachmentsList.Count > 0)
                        {
                            if (FileHelper.IsExistFile(HttpContext.Current.Server.MapPath(DelAttachmentsList.ElementAt(0).AttachmentsURL.Trim() + DelAttachmentsList.ElementAt(0).AttachmentsName.Trim())))
                            {
                                FileHelper.DeleteFile(HttpContext.Current.Server.MapPath(DelAttachmentsList.ElementAt(0).AttachmentsURL.Trim() + DelAttachmentsList.ElementAt(0).AttachmentsName.Trim()));
                            }
                            Attachments.Remove(DelAttachmentsList.ElementAt(0));
                            DelAttachmentsList.Remove(DelAttachmentsList.ElementAt(0));
                        }
                    }

                    if (InNewsPicSwfs != null && InNewsPicSwfs.Count > 0)
                    {
                        IList<InNewsPicSwf> DeInNewsPicList = InNewsPicSwfs.Where(a => a.IsDel == true).ToList();