List<string> 去重复 并且出现次数最多的排前面

  List<string> str = new List<string> {"a","b","a","a","c","b","c","c","d","c"};
                var tt = from ps in str 
                    group ps by ps 
                    into g
                    select new {g.Key,num=g.Count()};
                var newstr = tt.OrderByDescending(p => p.num);
                foreach (var item in newstr)
                {
                    Console.WriteLine(item.Key);
                }