/// <summary>        /// Save entity'propertity which is not null        /// </summary>        /// <typeparam name="T"></typeparam>        /// <param name="entity"></param>        public void SetModifyColumnsWithOutNull<T>(T entity) where T : EntityObject        {            ObjectStateEntry stateEntry = null;            bool isPresent = _ctx.ObjectStateManager.TryGetObjectStateEntry(entity, out stateEntry);            if (stateEntry == null)                _ctx.AttachTo(typeof(T).Name, entity);}錯(cuò)誤：An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.說(shuō)明：我是把上下文放在線程的CallContext里面了，在調(diào)用這個(gè)方法之前，我查詢過(guò)該對(duì)象，修改之后，調(diào)用這個(gè)方法進(jìn)行更新，結(jié)果報(bào)上述錯(cuò)誤。疑問(wèn)：既然從上下文中獲取不到對(duì)象狀態(tài)，那附加對(duì)象為何還是出錯(cuò)呢？請(qǐng)大蝦們賜教小弟