Question

Below I have table – Company

  id name value year
    1  IBM   10   2011
    2  IBM   30   2012
    3  IBM   10   2012
    4  C     10   2010

I want to group records by name and from each group return only one record with maximum id. All results combine into the list of companies using linq where year is greater 2011. For my example output should be – “3 IBM 10 2012”

I did write something but does not working.

var a = from x in companies where x.year > 2011
                  group x by new {x.name, x.value, x.ID, x.year } into g
                  select new {
                                  g.Key.name,
                                  g.Key.value,
                                  g.Max(a=>a.ID),
                                  g.Key.value
                              };
 return a.ToList();

Answer 1

Try this:

  var a = from x in companies
                where x.Year > 2011
                group x by new { x.Name } into g
                from x1 in companies
                where x1.ID == (from x2 in g select x2.ID).Max()
                select x1;   

Or something more efficient:

var a = from x in companies
                    where x.Year > 2011
                    group x by new { x.Name } into g
                    join x2 in companies on (from x3 in g select x3.ID).Max() equals x2.ID
                    select x2;