using System;

using System.Text.RegularExpressions;               

public class Program

{

    public static void Main()

    {

        foreach (Match ItemMatch in Regex.Matches("his it should search also X/X|3.20|S|0 string X|3.20|S|0 his string X|3.20|S|2x fsdf X|3.60|S|0 fd", 

                                                  @"\b((X/)?X\|[0-9]\.[0-9]{2}\|S\|[0-9]{1})\b"))

        {

            Console.WriteLine(ItemMatch);

        }

    }

}