linq 表分组后关联查询

测试linq，获取有教师名额的学校。比如学校有5个教师名额，teacher数量没超过5个，发现有空额
            var query = (from teacher in _repositoryTeacher.Table
                group teacher.Id by teacher.SchoolId
                into groupResult
                select new
                {
                    SchoolId = groupResult.Key,
                    Count = groupResult.Count()
                });

            var result = (from school in _repositorySchool.Table
                join teacher in query on school.Id equals teacher.SchoolId into  schoolAndTeachers
                from schoolAndTeacher in schoolAndTeachers.DefaultIfEmpty()
                where schoolAndTeacher==null || schoolAndTeacher.Count<school.TypeCode
                          select school).ToList();