using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        int[] numbers = new int[] { 1, 3, 5, 2, 7, 2 };

​

            var result = numbers.Select((v, i) => new { Value = v, Index = i })

                                .OrderByDescending(x => x.Value)

                                .Select(x => x.Index).ToArray();

​

            foreach (var item in result)

            {

                Console.WriteLine(item);

            }

    }

}