using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var texto = "N1N2S3S4L5L6O7O8X"; 

        var keys = texto.Zip(texto.Skip(1), (Key, Value) => new {Key, Value}).

            Where((pair, index) => index % 2 == 0)

            .Select(k => new KeyValuePair<string, string>(k.Key.ToString(), k.Value.ToString())); 

        foreach (var item in keys)

            Console.WriteLine(@"{{{0},{1}}}",item.Key,item.Value);}

}