Question

i have some table in dataBase. INV,LIB,TRAN_TT1 datatype all field in 3 table are string . i write this code

 var m = new MaterialModelContainer();
            var list = (from inv in m.INVs
                        where inv.NEW_QTY == "000000"
                        join lib in m.LIBs on inv.MESC equals lib.MESC
                        join tt1 in m.TRAN_TT1 on inv.MESC equals tt1.MESC4
                        where tt1.TYPE2 == "60" && tt1.QTY == "000000" 
                       select new
                                   {
                                       inv.MESC,
                                       lib.LINE_NO,
                                       lib.UNIT_LINE,
                                       Description = lib.DES + " " + lib.PART_NO,

                                   }).ToList();

table TRAN_TT1 has a ACTD field, i want get max value
i write this code

 var m = new MaterialModelContainer();
            var list = (from inv in m.INVs
                        where inv.NEW_QTY == "000000"
                        join lib in m.LIBs on inv.MESC equals lib.MESC
                        join tt1 in m.TRAN_TT1 on inv.MESC equals tt1.MESC4
                        where tt1.TYPE2 == "60" && tt1.QTY == "000000" 
                       select new
                                   {
                                       inv.MESC,
                                       lib.LINE_NO,
                                       lib.UNIT_LINE,
                                       Description = lib.DES + " " + lib.PART_NO,
                                     ACTD=  tt1.ACTD.Max()
                                   }).ToList();

but no work,

please help me to get max ACTD field . thanks all

Answer 1

Max is a aggregate function, and the aggregate functions in Linq has the same restrictions like in SQL – if you use aggregate function for one of the column – all other using columns should be also used in aggregate functions or you should use GroupBy by them.
So your sample should be something like:

var m = new MaterialModelContainer();
            var list = (from x in 

                       (from inv in m.INVs
                        where inv.NEW_QTY == "000000"
                        join lib in m.LIBs on inv.MESC equals lib.MESC
                        join tt1 in m.TRAN_TT1 on inv.MESC equals tt1.MESC4
                        where tt1.TYPE2 == "60" && tt1.QTY == "000000" 
                        select new {inv.MESC, lib.LINE_NO, lib.UNIT_LINE, Description = lib.DES + " " + lib.PART_NO, tt1.ACTD})

                        group by new {x.MESC, x.LINE_NO, x.UNIT_LINE, x.Description} into g
                        select new {g.Key.MESC, g.Key.LINE_NO, g.Key.UNIT_LINE, g.Key.Description, ACTDMax = g.Max(tt2 => tt2.ACTD) } );