//Linq

                     //var result = from p in personList

                     //             group p by p.Id

                     //    into grouped

                     //             select new { Id = grouped.Key, Count = grouped.Count() }

                     //    into temp

                     //             orderby temp.Count descending

                     //             select temp;

                     //Lambda

                     var result =

                         personList.GroupBy(g => g.Id)

                             .Select(s => new { Id = s.Key, Count = s.Count() })

                             .OrderByDescending(o => o.Count);