Linq GroupBy

                    //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);