Npgsql - EntityFramework - 未实现方法或操作

Question

我有这样的查询：

            var qHead = from x in context.anag_commessa1
                        join a in context.abe
                        on x.comcli equals a.abecod
                        where x.comcommtip == ward && x.comdatcon == delivery
                        orderby x.comprog descending
                        select new OrderHead
                        {
                            society = x.comsoci,
                            year = x.comanno,
                            letter = x.comlett,
                            order = x.comprog,
                            delivery = x.comdatcon,
                            customer_id = x.comcli,
                            customer_description = a.abers1,
                            destination = x.comdestin,
                            note = context.anag_commessa1_note.Where(o => o.ComSoci == x.comsoci && o.ComAnno == x.comanno && o.ComLett == x.comlett && o.ComProg == x.comprog).Select(o=>o.ComNote).FirstOrDefault() ?? ""
                        };

如果我执行实体框架提供程序它工作，用Npgsql返回错误，方法或操作没有实现