using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Person> persons = new List<Person>();
            persons.Add(new Person { Age = 1, Score = 20 });
            persons.Add(new Person { Age = 2, Score = 20 });
            persons.Add(new Person { Age = 3, Score = 20 });
            persons.Add(new Person { Age = 4, Score = 30 });
            persons.Add(new Person { Age = 5, Score = 40 });
            persons.Add(new Person { Age = 6, Score = 50 });
            persons.Add(new Person { Age = 7, Score = 60 });
            persons.Add(new Person { Age = 8, Score = 60 });
            persons.Add(new Person { Age = 9, Score = 60 });
            persons.Add(new Person { Age = 10, Score = 70 });
            persons.Add(new Person { Age = 11, Score = 70 });
            persons.Add(new Person { Age = 12, Score = 80 });
            var test = persons.GroupBy(a => a.Score)
												.OrderByDescending(a => a.Key)
												.SelectMany(a => a.OrderBy(b => Guid.NewGuid()))
												.ToList();
            Console.Read();
        }
    }
    public class Person
    {
        public int Age { get; set; }
        public int Score { get; set; }
    }
}