Applied XML Programming for Microsoft .NET.pdf - Csbdu.in

the type. In addition, attributes and namespaces also have ad hoc methods to returntheir values: GetAttribute and GetNamespace.When you call either MoveToFirstNamespace or MoveToNextNamespace, you canspecify an argument of type XPathNamespaceScope. The XPathNamespaceScopeenumeration has three values: All, ExcludeXML, and Local. All returns all namespacesdefined in the scope of the current node, including xmlns:xml, which is alwaysdeclared implicitly. ExcludeXml returns all namespaces defined in the scope of thecurrent node, excluding xmlns:xml. Local returns all namespaces that are definedlocally at the current node. Whatever value you specify, the order of the namespacesreturned is not defined. A namespace node is a special type of attribute node. Whenselected, the navigator's Name property returns the namespace prefix. The Valueproperty, on the other hand, returns the URI.Table 6-5 lists the XPathNavigator class's methods for selecting nodes through XPathqueries.Table 6-5: XPathNavigator' Selection MethodsMethodSelectSelectAncestorsSelectChildrenSelectDescendantsDescriptionReturns the node-set selected by the specified XPathexpression. The context for the selection is theposition of the navigator when the method is called.The XPath expression can be passed in as plain textor in a compiled form.Selects all the ancestor element nodes of the currentnode. You can narrow the returned node-set byspecifying a node name and a namespace URI tomatch.Selects all the child nodes of the current node. Youcan narrow the node-set by specifying a node nameand a namespace URI to match. Attributes andnamespace nodes are not included.Selects all the descendant nodes of the current node.You can narrow the node-set by specifying a nodename and a namespace URI to match. Attributes andnamespace nodes are not included.None of these methods produces any effect on the state of the XPathNavigator object.The following code snippet demonstrates how to select the descendants of a node. Thecode to get the ancestors is nearly identical.// Create the underlying XPath-enabled document objectXPathDocument doc = new XPathDocument(fileName);// Create the navigator for the specified objectXPathNavigator nav = doc.CreateNavigator();// Select the descendants of the current node that match// the specified criterianav.SelectDescendants(nodeName, nsUri, selfIncluded);222