Grouping with Max Linq ASP.NET C# - without model or entity

  var dt = GridView1.DataSource as DataTable;

                var a= dt.AsEnumerable().GroupBy(s => s.Field<string>("Discipline").ToString());

                

                

                //dt.DefaultView.Sort = sort;

                var final = dt.AsEnumerable().GroupBy(x => x.Field<string>("Discipline"), (key, g) => g.OrderByDescending(s => s.Field<Int64>("ID")).First()).Select(t=>t.Field<Int64>("ID"));

                var tt = final.ToList();

                

                if(tt.Exists(o=> o == Convert.ToInt64(DataBinder.Eval(e.Row.DataItem, "ID"))))

                        {

                    e.Row.BackColor = System.Drawing.ColorTranslator.FromHtml("#0000ff");

                }

reference:-https://stackoverflow.com/questions/35170408/linq-how-to-get-the-max-id-with-a-group-by-clause