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copied!<p>This answer summarizes my entry on the Australian Delphi User's Group blog, <a href="http://members.adug.org.au/2012/08/17" rel="nofollow">"Dances with XML"</a>. Refer to it if you need further detail.</p> <h2>Access to nodes via XML</h2> <p>You are headed in the right direction, by trying to leverage XPATH as an easy mechanism to access and navigate through an XML document. It just that your implementation needs a bit of polishing. Demonstrative code is shown below.</p> <h2>Q1 How can I easily check if a given object exists?</h2> <p>Use the 'in' operator with an XPATH expression, and the referenced "Dances with XML" utility unit. For example with your supplied input document, this code fragment tests if a control node exists with a</p> <pre><code>if 'role/access/control[type="group"]' in XFocus(Root) then ShowMessage(' Hello! I''m here.') </code></pre> <p>...where Root is the document root node.</p> <h2>Q2 How can I easily add an item of type group or user?</h2> <p>For adding stuff, an XML library with a fluent API would be best, but you can achieve semi-fluency with the following methods:</p> <h3>Add a child element</h3> <p>To add a child element use code like this...</p> <pre><code>ParentNode.AddChild('child-name') </code></pre> <p>This is semi-fluent because this above expression is a function which returns IXMLNode.</p> <h3>Add an attribute</h3> <p>To add a new attribute, or change an existing one use code like this...</p> <pre><code>ElementNode.Attributes['myattrib'] := 'attrib-value' </code></pre> <p>There is no native idempotent version of this functionality, but it would be trivial to roll your own.</p> <h2>Example 1</h2> <p>This example roughly replicates the functionality of the OP's Test() procedure given in the question.</p> <pre><code>// uses uXMLUtils from referenced demo. procedure Test; begin Doc := LoadDocument_MSXML_FromStream( TestXMLStream); Root := Doc.Node; // To test if control node exists: if 'role/access/control' in XFocus(Root) then ShowMessage('The control node exists!'); // To access each control node: for ControlNode in 'role/access/control' then DoSomethingForEachControlNode( ControlNode); // To access on the first control node: for ControlNode in '(role/access/control)[1]' then DoSomethingForFirstControlNode( ControlNode); // To access on the first control node which has BOTH group type and Admin object: for ControlNode in '(role/access/control[type="group"][object="COMPUTER\Administrators"])[1]' do DoSomething( ControlNode); // To do something for EACH control node which is EITHER group type or Admin object: for ControlNode in 'role/access/control[type="group" or object="COMPUTER\Administrators"]' do DoSomething( ControlNode); </code></pre> <p>end;</p> <h2>Example 2</h2> <p>Let's say we want to add a computer administrators group, but only if one does not already exist. If adding, the new nodes go under a new access node. We can achieve this with a trivial amount of code if we leverage XPATH. This is shown in the code fragment below.</p> <pre><code>if not 'role/access/control[type[.="group"][object[.="COMPUTER\Administrators"]]' in XFocus(Root) then begin ControlNode := Root.ChildNodes.FindNode('role') .AddChild(['access') .AddChild('control'); ControlNode.AddChild('type' ).Text := 'group'; ControlNode.AddChild('object').Text := 'COMPUTER\Administrators' end; </code></pre>

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