How to run XPath Query in Delphi using MSXML DOM?

How to run XPath Query in Delphi using MSXML DOM?

This article illustrates a simple example on how to run XPath query to XML file in Delphi by using MSXML DOM. XPath Query is used to select a certain subset of the XML. XPath, the XML Path Language, is a query language for selecting nodes from an XML document. In addition, XPath may be used to compute values from the content of an XML document. XPath was defined by the World Wide Web Consortium. We will try to locate the value for <Link role="self"> in the following XML File using a XPath query. 

Sample XML file

<ResourceSet>

    <Resources>

        <Id>ID</Id>

        <Link role="self">http://theprofessionalspoint.blogspot.com/</Link>

        <Status>Pending</Status>            

    </Resources>

</ResourceSet>

Following is a simple Delphi function to located the value in the node "Link" under attribute "role".

function TForm1.RunXPathQueryInDelphi(XMLFilename : string): string;

var

  iNode : IDOMNode;

  Sel: IDOMNodeSelect;

begin

  try

    XMLDoc.Active := False;

    XMLDoc.FileName := XMLFilename;

    XMLDoc.Active := True;

    Sel := XMLDoc.DOMDocument as IDomNodeSelect;

    Result := '';

    iNode := Sel.selectNode('//Link[@role = "self"]');  //XPath Query

    if Assigned(iNode) then

      if (not VarisNull(iNode.NodeValue)) then

        Result := iNode.NodeValue;

    XMLDoc.Active := False;

  Except on E: Exception do

    begin

      MessageDlg(E.ClassName + ': ' + E.Message, mtError, [mbOK], 0);

      LogEvent(E.Message);

    end;

  end;

end;