using System;

using System.Text.RegularExpressions;

public class Program

{

    //static Regex rxNonDigits = new Regex( @"[^\d]+");

    static Regex extendedCharacterSet = new Regex( "[^a-zA-Z0-9+\\.\\ \\!\\&\\'\\(\\)\\*\\+\\,\\-\\.\\/\\:\\;\\?\\=\\~\\@\\[\\]\\{\\}\\\\|\\<\\>\\#\"]+");

    public static void Main()

    {

        //String regExString = "/[^w+\\.\\ \\!\\&\\'\\(\\)\\*\\+\\,\\-\\.\\/\\:\\;\\?\\=\\~\\@\\[\\]\\{\\}\\\\|\\<\\>\\#\"]+/g";

        //String regExString = "/[^a-z0-9]+/g";

        String testStr = "ABC€£123def";

        //String notes = Regex.Replace(testStr, regExString, "");

        var notes = StripNonDigits(testStr);

        Console.WriteLine(notes);

    //

    }

    public static string StripNonDigits( string s )

    {

        return extendedCharacterSet.Replace(s,"") ;

    }

}