LINQ group 两个表

CCPressDataContext cp = new CCPressDataContext();
            var ee = from e in cp.ACC_BookFactCost
                     select e;
            if (CTN != "")
            {
                ee = ee.Where(x => x.ChoiceThemeNo.Contains(CTN));
            }
            if (BookNo != "")
            {
                ee = ee.Where(x => x.COM_BookInfoOne.BookNo.Contains(BookNo));
            }
            if (BookName != "")
            {
                ee = ee.Where(x => x.COM_BookInfoOne.BookName.Contains(BookName));
            }
            if (department != "")
            {
                ee = ee.Where(x => x.COM_BookInfoOne.COM_Departments.DepartmentName.Contains(department));
            }
            if (ZB != "")
            {
                ee = ee.Where(x => x.COM_BookInfoOne.ResponsibleEditor.Contains(ZB));
            }
            if (start != "")
            {
                ee = ee.Where(x => Convert.ToInt32(x.AccountPeriod)>=Convert.ToInt32(start));
            }
            if (end != "")
            {
                ee = ee.Where(x => Convert.ToInt32(x.AccountPeriod) <= Convert.ToInt32(end));
            }
            var aa = from a in ee
                     group a by a.ChoiceThemeNo into g
                     select new { ChoiceThemeNo = g.Key, M1 = g.Sum(x => x.M1), M2 = g.Sum(x => x.M2), M3 = g.Sum(x => x.M3), M4 = g.Sum(x => x.M4), M5 = g.Sum(x => x.M5), M6 = g.Sum(x => x.M6), M7 = g.Sum(x => x.M7), M8 = g.Sum(x => x.M8), M9 = g.Sum(x => x.M9), M10 = g.Sum(x => x.M10), M11 = g.Sum(x => x.M11), M12 = g.Sum(x => x.M12), M13 = g.Sum(x => x.M13), M14 = g.Sum(x => x.M14), M15 = g.Sum(x => x.M15), M16 = g.Sum(x => x.M16), M17 = g.Sum(x => x.M17) ,BookInfo=from b in cp.COM_BookInfoOne where b.ChoiceThemeNo==g.Key select b
                                };

            return aa;