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

You can specify other settings for the parser context using the properties of theXmlParserContext class, including Encoding, BaseURI, and DocTypeName. Inparticular, BaseURI is especially useful because it indicates the location from which thefragment was loaded.Writing a Custom XML ReaderWe have one more topic to consider on the subject of XML readers, which opens up awhole new world of opportunities: creating customized XML readers. An XML readerclass is merely a programming interface for reading data that appears to be XML. TheXmlTextReader class represents the simplest and the fastest of all possible XMLreaders but—and this is what really matters—it is just one reader. Its inherent simplicityand effectiveness stems from two key points. First, the class operates as a read-only,forward-only, nonvalidating parser. Second, the class is assumed to work on nativeXML data. It has no need, and no subsequent overhead, to map input data internally toXML data structures.Virtually any data can be read, traversed, and queried as XML as long as a tailor-madepiece of code takes care of mapping that data to an XML Schema. This mapping codecan then be buried in a method that simply returns one of the standard reader objectsor creates a custom XML reader class.NoteWhat's the advantage of exposing data through XML? XML providesa kind of universal model for defining a set of information (infoset),the type and layout of constituent items (XML Schema), and thequery commands (XPath). In the .NET Framework, XML readersprovide an effective way to deal with hierarchical, XML-shaped data.Because XML is just a metalanguage used to describe information,and not a data repository itself, the key difference between standardXML readers and custom XML readers is in the location and themodality of intervention of the code that exposes data as XML. Suchcode is not part of the basic .NET XML reader classes butconstitutes the core of custom XML readers.Mapping Data Structures to XML NodesFor a long time, INI files have been a fundamental part of Microsoft Windowsapplications. Although with the advent of Microsoft Win32 they were officially declaredobsolete, a lot of applications have not yet stopped using them. Understanding thereasons for this persistence is not of much importance here, but when they weredesigning the .NET Framework, the Microsoft architects decided not to insert anymanaged classes to handle INI files. Although overall I agree with their decision, keepin mind that if you need to access INI files from within a .NET Framework application,you'll find at your disposal only workarounds, not a direct solution.You could, for instance, read and write the content of an INI file using file and I/Oclasses, or you might resort to making calls to the underlying Win32 unmanagedplatform. Recently, however, I came across a rather illuminating MSDN article in whichan even better approach is discussed. (See the section "Further Reading," on page 74,for details and the URL.) The idea is this: Why not wrap the contents of INI files into anXML reader? INI files are not well-formed XML files, but a custom reader could easilymap the contents of an INI file's sections and entries to XML nodes and attributes.45