using System;

using System.Collections.Generic;   

using System.Linq;

public class Program

{

    public static void Main()

    {

        var myList = new List<int> {1, 2, 5, 2, 2 , 7};

        var mostfrequent = myList.GroupBy(i=>i).OrderByDescending(grp=>grp.Count())

         .Select(grp=>grp.Key).First();

        Console.WriteLine(mostfrequent);

    }

}