using System;

​

using System.Collections.Generic;

using System.Text.RegularExpressions;

​

​

public class Program

{

    public static void Main()

    {

        var t = "G9906QZN^SXרK9_TUCE[10F5-CB2C1DA9D24A.hello";

​

    List<string> lst = new List<string>();

    foreach (char element in t)

    {

        if (char.IsDigit(element) || char.IsLetter(element)) lst.Add(@"\w");

        else  lst.Add(@"\"+element);

​

    }

    Console.WriteLine(string.Join("", lst.ToArray()));

​

    //Console.WriteLine(Regex.Replace(Regex.Escape(t), @"((?!_)\w)+", m => $@"(?:[^_]{{{m.Length}}})\w{{{m.Length}}}"));

    //var rgx = Regex.Replace(Regex.Escape(t), @"[a-z0-9]+", m => @"[a-z0-9]{" + m.Length + "}",RegexOptions.IgnoreCase);

​

    var rgx = Regex.Replace(Regex.Escape(t),    @"((?!_)\w)+", m => $@"(?:[^_]{{{m.Length}}})\w{{{m.Length}}}");

​

    Console.WriteLine(rgx);

​

​

    //check backwords

    Regex regex = new Regex(rgx, RegexOptions.IgnoreCase);

    Match match = regex.Match(t);

    if (match.Success)

    {

        Console.WriteLine(match.Value);

    }

else Console.WriteLine("xxxxxxxxxx");

    }

}