/// 只更新storedAddress数据中的DefaultAddress字段,更新为false         /// 将默认地址改为不是默认地址          /// </summary>          /// <param name="id">需要修改的对象的id</param>          public void Update(int id)          {              StoredAddress s = new StoredAddress { StoredAddressID = id };             object originalItem = null;             System.Data.EntityKey key = _context.CreateEntityKey("StoredAddresses", s);             if (_context.TryGetObjectByKey(key, out originalItem))             {                 _context.Detach(originalItem);             }              s.DefaultAddress = true;              _context.StoredAddresses.Attach(s);                s.DefaultAddress = false;                          _context.SaveChanges();              _context.Detach(s);         }