using System;

using System.Text;

using System.Collections.Generic;

​

public class Program

{

    public static IEnumerable<string> ReverseSplit(string input, int limit = 6)

    {

        var temp = new StringBuilder();

        for (int i = input.Length - 1; i >= 0; i--)

        {

            if (input[i] == '_' && limit > 0)

            {

                yield return temp.ToString();

                temp.Clear();

                limit--;

            }

            else

            {

                temp.Insert(0, input[i]);

            }

        }

        if (temp.Length > 0)

            yield return temp.ToString();

    }

    public static void Main()

    {

        var input = "Name_with_underscore_specific_SiteID_CountryID_PageID_DeviceID_PageName";

        foreach (var data in ReverseSplit(input))

        {

            Console.WriteLine(data);

        }

    }

}