Something

    protected string PrepareBoldifyRegex(List<string> Terms)
    {
        if (Terms.Count <= 0) return "";
        string bigfuckingregex = "";
        Terms.Sort(new LengthComparer());
        foreach (string Term in Terms)
        {
            if (Term.Length != 0)
                bigfuckingregex += "(\\b" + Regex.Escape(Term) + "(|s|es)\\b)|";
        }
        bigfuckingregex = bigfuckingregex.Substring(0, bigfuckingregex.Length - 1);
        return bigfuckingregex;
    }