Apostrophe in XML string

1

I just did a bug fix on our XML exporter to handle illegal characters - my initial research determined that ampersands , greater thans, less thans and double quotes have to be dealt with before adding them to a string in an XML line.

I successfully implemented this only to discover that a single quote is also an illegal XML character.

How do you deal with the double whammy of Delphi and XML to deal with this?

// for XML
// & = &
// < = <
// > = >
// " = "
// ’ = ’ // oh no
// cIllegalXmlChars = ‘&<>"’;

regards

Brian

2

This is my goto code for this

function IsValidXMLChar(wc: WideChar): Boolean;
begin
  case Word(wc) of
    $0009, $000A, $000C, $000D,
      $0020..$D7FF,
      $E000..$FFFD, // Standard Unicode chars below $FFFF
      $D800..$DBFF, // High surrogate of Unicode character  = $10000 - $10FFFF
      $DC00..$DFFF: // Low surrogate of Unicode character  = $10000 - $10FFFF
      result := True;
  else
    result := False;
  end;
end;

function StripInvalidXML(const s: string): string;
var
  i, count: Integer;
begin
  count := Length(s);
  setLength(result, count);
  for i := 1 to Count do // Iterate
  begin
    if IsValidXMLChar(WideChar(s[i])) then
      result[i] := s[i]
    else
      result[i] := ' ';
  end; // for}
end;


function EscapeForXML(const value: string; const isAttribute: boolean = True; const isCDATASection : Boolean = False): string;
begin
  result := StripInvalidXML(value);
  if isCDATASection  then
  begin
    Result := StringReplace(Result, ']]>', ']>',[rfReplaceAll]);
    exit;
  end;

  //note we are avoiding replacing &amp; with &amp;amp; !!
  Result := StringReplace(result, '&amp;', '[[-xy-amp--]]',[rfReplaceAll]);
  Result := StringReplace(result, '&', '&amp;',[rfReplaceAll]);
  Result := StringReplace(result, '[[-xy-amp--]]', '&amp;amp;',[rfReplaceAll]);
  Result := StringReplace(result, '<', '&lt;',[rfReplaceAll]);
  Result := StringReplace(result, '>', '&gt;',[rfReplaceAll]);

  if isAttribute then
  begin
    Result := StringReplace(result, '''', '&#39;',[rfReplaceAll]);
    Result := StringReplace(result, '"', '&quot;',[rfReplaceAll]);
  end;
end;

Probably not the most efficient but has been working fine in FinalBuilder for years (XE7 - won’t work for non unicode versions) .

3

Quotes and apostrophes are only illegal in tags and attributes content, not text. See also useful tips in The XML FAQ: What are the special characters in XML?.
I personally use utf-8 notation for special characters (& < >)
Regards,

Didier