Reading distinct values from XML using XPath

Question

I have an XML in the following format:

<Accounts>
   <Account Number="1"   DebitAmount="1000" Amount="2827561.95" /> 
   <Account Number="225" DebitAmount="2000"  Amount="12312.00" /> 
   <Account Number="236" DebitAmount="London"    Amount="457656.00" /> 
   <Account Number="225" DebitAmount="London"    Amount="23462.40" /> 
   <Account Number="236" DebitAmount="Bangalore" Amount="2345345.00" /> 
</Accounts>

How do I retreive the unique Account Numbers using Xpath? ie, I want to get the values 1, 225 and 236.

This is what I did:(I'm using Delphi 2007...)

Const XmlStr =
' <Accounts>
   <Account Number="1"   DebitAmount="1000" Amount="2827561.95" /> 
   <Account Number="225" DebitAmount="2000"  Amount="12312.00" /> 
   <Account Number="236" DebitAmount="London"    Amount="457656.00" /> 
   <Account Number="225" DebitAmount="London"    Amount="23462.40" /> 
   <Account Number="236" DebitAmount="Bangalore" Amount="2345345.00" /> 
</Accounts>';

 function GetAccountNumbers:TList;
 Var
   XMLDOMDocument  : IXMLDOMDocument;
   accounts : IXMLDOMNodeList;
  accountdetail :IXMLDOMNode;
   i:Integer
   list :TList
 begin
   Result:=TList.Create;
   XMLDOMDocument:=CoDOMDocument.Create;
   XMLDOMDocument.loadXML(XmlStr);
   accounts:= XMLDOMDocument.SelectNodes(''./Accounts 
  /Account[not(@Number=preceding-sibling/ Account /@Number)]');
  for i := 0 to accountdetails.length - 1 do begin
     accountdetail := accountdetails.item[i];
     //omitting the "<>nil" checks...
     list.Add(accountdetail.attributes.getNamedItem('Number').Nodevalue;
  end;
 end;

But this returns no nodes(accountdetails.length=0). Please let me know what I am missing here.

Thanks,

Pradeep

Answer 1

It seems the version of the MSXML from Delphi 2007 doesn't support XPath axis. So if you decide to use the following code, import either Microsoft XML, v3.0 or the Microsoft XML, v6.0 type library first and then try this:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, MSXML2_TLB;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

const
  XMLString =
    '<Accounts>' +
    '<Account Number="1" DebitAmount="1000" Amount="2827561.95"/>' +
    '<Account Number="225" DebitAmount="2000"  Amount="12312.00"/>' +
    '<Account Number="236" DebitAmount="London" Amount="457656.00"/>' +
    '<Account Number="225" DebitAmount="London" Amount="23462.40"/>' +
    '<Account Number="236" DebitAmount="Bangalore" Amount="2345345.00"/>' +
    '</Accounts>';

type
  TIntegerArray = array of Integer;

function GetAccountNumbers(const AXMLString: string): TIntegerArray;
var
  I: Integer;
  XMLDOMNodeList: IXMLDOMNodeList;
  XMLDOMDocument: IXMLDOMDocument3;
begin
  XMLDOMDocument := CoDOMDocument60.Create;
  if Assigned(XMLDOMDocument) and XMLDOMDocument.loadXML(AXMLString) then
  begin
    XMLDOMNodeList := XMLDOMDocument.selectNodes('/Accounts/Account[not(@Number=preceding-sibling::Account/@Number)]/@Number');
    SetLength(Result, XMLDOMNodeList.length);
    for I := 0 to XMLDOMNodeList.length - 1 do
      Result[I] := XMLDOMNodeList.item[I].nodeValue;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  S: string;
  I: Integer;
  IntegerArray: TIntegerArray;
begin
  S := 'Account numbers: ';
  IntegerArray := GetAccountNumbers(XMLString);
  for I := 0 to Length(IntegerArray) - 1 do
    S := S + IntToStr(IntegerArray[I]) + ', ';
  Delete(S, Length(S) - 1, 2);
  ShowMessage(S);
end;

end.