How to use group by with multiple table joins in EF Core

am trying to convert below query in entity framework core but not able to access field in select query after apply group by.

 

Select ProdCatg.Category As [Category] ,Prod.FKProdCatgID As [FKProdCatgID] ,SUM(Dtl.Qty + LD.ProdConv1 + Trn.CashAmt ) As [DistributionRateValue] From tblSalesInv_Dtl Dtl Left Join tblSalesInv_Trn Trn on Trn.PKID=Dtl.FKID And Trn.FKSeriesID=Dtl.FKSeriesID Left Join tblProdLot_Dtl LD on Dtl.FKLotID=LD.PKLotID And LD.FKProdID=Dtl.FKProdID Left Join tblProd_Mas Prod ON PKProdID=Dtl.FKProdID Left Join tblProdCatg_Mas ProdCatg On PKProdCatgID=Prod.FKProdCatgID Where Trn.DraftMode=0 Group By Prod.FKProdCatgID,ProdCatg.Category Order By Category

 

I am trying convert like this but but not able to access Dtl.Qty + LD.ProdConv1 + Trn.CashAmtfields

 

var result1 = (from dtl in _context.TblSalesInvDtl join ser in lstSeries on dtl.FkseriesId equals ser join trn in _context.TblSalesInvTrn on new { s1 = dtl.Fkid, s2 = ser } equals new { s1 = trn.Pkid, s2 = trn.FkseriesId } join lot in _context.TblProdLotDtl on new { s1 = dtl.FklotId, s2 = dtl.FkprodId } equals new { s1 = lot.PklotId, s2 = lot.FkprodId } join p in _context.TblProdMas on dtl.FkprodId equals p.PkprodId into pr from Prod in pr.DefaultIfEmpty() join pl in _context.TblProdMas on dtl.FklinkedProdId equals pl.PkprodId into plid from ProdLinked in plid.DefaultIfEmpty() join t in _context.TblTaxMas on dtl.FktaxId equals t.PktaxId into tid from Tax in tid.DefaultIfEmpty() join c in _context.TblProdCatgMas on Prod.FkprodCatgId equals c.PkprodCatgId into cid from Catg in cid.DefaultIfEmpty() where trn.EntryDate == Convert.ToDateTime("1-12-2018") group Catg by new { Prod.FkprodCatgId, Catg.Category } into gb //, dtl, lot, Prod select new { CategoryName = gb.FirstOrDefault().Category, DistributionRateValue = gb.Sum(a => (gb.Key.dtl.Qty + gb.Key.lot.ProdConv1+ gb.Key.lot.CashAmt)), FKProdCatgID= gb.Key.Prod.FkprodCatgId, } ).ToList();

 

can anybody help me how can I access multiple table fields in sum with groupby in entity framework core.