错误：无法删除对象，因为在ObjectStateManager中找不到该对象

Question

public void Delete(IList<WsrteTestBasketRequest> wsrteTestBasketRequests)
        {

            using (var unitOfWork = new WsrteUnitOfWork(new WsrteContext()))
            {

                foreach (var request in wsrteTestBasketRequests)
                {

                    request.State = ObjectState.Deleted;
                    unitOfWork.WsrteBasketRequests.Remove(request);
                }
                unitOfWork.Complete();

            }
        }

在remove方法中，代码抛出错误。无法删除该对象，因为在ObjectStateManager中找不到该对象。抓我的头。