using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        int[] numbers = new int[] { 5, 1, 9, 2, 3, 7, 4, 5, 6, 8, 7, 6, 3, 4, 5, 2 };  

​

        var groupOfNumbers= numbers.GroupBy(x => x).Select(num => new { key = num.Key, count = num.Count()}).OrderByDescending(x => x.key).ToList();

​

        foreach(var element in groupOfNumbers)

        {

            Console.WriteLine($"Key: {element.key}, count: {element.count}");

        }

    }

}