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

First, decoupling data containers from navigators, and navigators from iterators,represents a good bargain from the software standpoint. The ultimate reason forkeeping the navigation and the iteration API distinct, however, is that in this way theresults of any XPath query can be easily accessed and processed from differentprogramming environments—XML DOM, XPath, and, last but not least, XSLT.The XPathNodeIterator ClassThe XPathNodeIterator class has no public constructor and can be created only by theparent navigator object. The iterator provides forward-only access to the nodesselected by XPath query. Callers use the iterator's methods and properties to access allthe nodes included in the node-set. Figure 6-7 illustrates the relationship betweencallers, navigators, and iterators. A caller passes an XPath expression. The navigatorexecutes the command and gets a node-set. The caller then receives an iterator objectto access the members of the node-set. Current, Count, and MoveNext are the keymembers of the iterator's programming interface.Figure 6-7: The relationship between callers, navigators, and iterators.Properties of the Iterator ObjectTable 6-10 summarizes the properties exposed by the XPathNodeIterator class.Table 6-10: Properties of the XPathNodeIterator ClassPropertyCountCurrentDescriptionReturns the number of elements in the node-set. Thisvalue refers to the top-level nodes and does not considerchild nodes.Returns a reference to a navigator object rooted in the233