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

.NET XML writers only ensure the well-formedness of each individual XML elementbeing generated. Writers can in no way guarantee the well-formedness of the entiredocument and can do even less to validate a document against a DTD or a schema.Although badly formed XML documents can only result from actual gross programmingerrors, the need for an extra step of validation is often felt in production environments,especially when the creation of the document depends on a number of variable factorsand run-time conditions. For this reason, we've also examined the key points involvedin the design and implementation of a validating XML writer.This chapter also featured a few custom XML-driven writers. In this chapter, youlearned how to write string arrays, JPEG images, and DataTable objects to specificXML schemas. It goes without saying that the techniques discussed here do notexhaust the options available in the .NET Framework for those tasks. For example, theXML serializer can sometimes be more effectively employed to obtain the same results.(XML serializers are covered in Chapter 11.)These examples were provided with a double goal: to show one way to solve aproblem, and to demonstrate custom XML writers. As a general guideline, bear in mindthat the more specific an XML-based format is, the more a specialized writer class canhelp. The key advantage of a writer class is perhaps not so much raw performancesavings but the resultant elegance, reusability, and efficiency of the design.We've also looked at an intermediate level of XML parser that falls somewhere betweenstreaming parsers such as readers and XML DOM. XML readers are great for parsingXML documents, but they work in a read-only way. XML DOM parsers, on the otherhand, make updating documents a snap—but only after the documents have been fullyloaded in memory. The XmlTextReadWriter class incorporates a reader and a writerand coordinates their independent activity through a simple new API. As a result, youcan parse a document one node at a time while maintaining the ability to add, update,or delete nodes. The new class is not the cure-all for any XML pains, but it can be aninteresting option in some situations.In Chapter 5, we'll examine the XML DOM classes that you must use when fullread/write access to XML documents is critical and when the ability to perform searchestakes precedence over the memory footprint.Further ReadingThis chapter touches on a number of topics that you might want to know more about.Some are XML-related, but not so much .NET-related as to find an ideal place fordiscussion here. Some are not really XML-related but definitely belong to the .NETFramework and, as such, deserve at least a reference here.One topic we spent a lot of time on in this chapter is XML namespaces and qualifiednames. The official site where the specification can be found ishttp://www.w3.org/TR/REC-xml-names. In Chapter 3, I covered XML validation and thevarious schema involved in the process. If you think you need an XML crash coursefrom a higher, non-.NET-Framework-related perspective, I can recommend two books.One is Essential XML, by Don Box, John Lam, and Aaron Skonnard (Addison-Wesley,2000). This reference is great if you need to get the gist of XML in a platformindependentand language-independent context. Otherwise, look at the XMLProgramming Core Reference, by R. Allen Wyke, Sultan Rehman, Brad Leupen, andAsh Rofail (Microsoft Press, 2002), for more development-related considerations andtips.A great source for learning about underdocumented features and tricks of the .NETFramework is certainly Jeffrey Richter's most recent book, Applied .NET FrameworkProgramming (Microsoft Press, 2002). This book is a gold mine for all that boring stuff166