Entity Framework 4.0 怎么更新对象

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();

                        while (DeInNewsPicList.Count > 0)
                        {

                            if (FileHelper.IsExistFile(HttpContext.Current.Server.MapPath(DeInNewsPicList.ElementAt(0).FileURL.Trim() + DeInNewsPicList.ElementAt(0).FileName.Trim())))
                            {

                                FileHelper.DeleteFile(HttpContext.Current.Server.MapPath(DeInNewsPicList.ElementAt(0).FileURL.Trim() + DeInNewsPicList.ElementAt(0).FileName.Trim()));

                            }
                            InNewsPicSwfs.Remove(DeInNewsPicList.ElementAt(0));
                            DeInNewsPicList.Remove(DeInNewsPicList.ElementAt(0));
                        }
                    }

                    nd.NewDocAttachments = Attachments;
                    nd.InNewsPicSwf = InNewsPicSwfs;
                    
                    如何将nd 更新到库里？   
                    db里有NewsDoc 表属性，NewsDoc里又包括两个列表属性NewDocAttachments ,
InNewsPicSwf ,分别为与NewsDoc的相关联的表。                 return db.SaveChanges();
                }

            }
            catch (Exception ex)
            {
                Log4Helper.ErrorFormat(CommonParameters.ErrorMessage, "更新NewsDoc", ex.Message, ex.StackTrace);
                throw ex;
            }
        }

Entity?Framework?4 更新对象?
[解决办法]
上了一坨代码,不知道你想问什么
[解决办法]
直接查询DataContext得到对象，修改它的属性，最后调用DataContext.SaveChanges()方法即可。
[解决办法]
你看看你的context是不是ObjectContext
如果是
把objectContext变成DbContext
public DbContext(ObjectContext objectContext,
bool dbContextOwnsObjectContext)
{}