in this code this line is not working

   return ("" + m.Value + "");

suppose m="Delhi"

output screen it is print as "Delhi


  public string HighlightText(string InputTxt)
  {
  string Search_Str = FilterSearchTerms.Text;
  // Setup the regular expression and add the Or operator.
  Regex RegExp = new Regex(Search_Str.Replace(" ", "|").Trim(), RegexOptions.IgnoreCase);
  // Highlight keywords by calling the
  //delegate each time a keyword is found.
  return RegExp.Replace(InputTxt, new MatchEvaluator(ReplaceKeyWords));
  }

  public string ReplaceKeyWords(Match m)
  {

  //  return ( m.Value);
  return ("" + m.Value + "");
  }