Hi Paulo, you gave the answer yourself :)
The easiest way to do it is with the replace() function.

Replace(Replace(Replace(Replace(Replace(message,"á","a"),"à","a"),"ã","a),"â","a",)"é","e") (... and so on)

If you feel 1337 today and would like to do this dinamically... You can always build an extension.

static string RemoveDiacritics(string stIn) {
  string stFormD = stIn.Normalize(NormalizationForm.FormD);
  StringBuilder sb = new StringBuilder();

  for(int ich = 0; ich < stFormD.Length; ich++) {
    UnicodeCategory uc = CharUnicodeInfo.GetUnicodeCategory(stFormD[ich]);
    if(uc != UnicodeCategory.NonSpacingMark) {
      sb.Append(stFormD[ich]);
    }
  }

  return(sb.ToString().Normalize(NormalizationForm.FormC));
}

Source: stackoverflow

:)

Don't think I went this 1337 - https://en.wikipedia.org/wiki/Leet - but, definitely went somewhere.

XIF .Net Version of the code referenced by @António Chinita here