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

The data island is created using the server control, which reads a previouslycreated XML file. The employees.xml file is simply the XML normal form of a DataSetobject. The DataSet object is serialized to the data island, and the page is sent to thebrowser. On the client, some Javascript code takes care of extracting the data islandcontents as XML text and passing it on to a method—Load—on the managed control.Internally, the Load method rebuilds the DataSet object and uses it to populate its ownuser interface. Figure 14-4 shows the ASP.NET page in action, with a filter applied andwith the data sorted in ascending order by last name.Figure 14-4: Sorting and filtering data on the client.NoteWhen embedding script code in Web pages to be consumed overthe Internet, you should use the Javascript language to reach thewidest possible range of browsers. VBScript is limited to InternetExplorer. In this example, however, we're making seriousassumptions about the capabilities of the client—.NET Frameworkinstalled, support for the extended syntax of the tag, andability to host managed code. This means that your browser mustbe Internet Explorer 5.5 or, more likely, Internet Explorer 6.0 orlater. So in this case you can reasonably drop Javascript in favor ofVBScript.From MSXML Documents to .NET XML DocumentsWhen Internet Explorer detects the tag in a client page, it automatically extractsthe page's contents, creates an internal instance of the MSXML parser, and makes thedata available through an XMLDOMDocument object. Note that XMLDOMDocument isnot a managed object created from any of the .NET Framework classes but rather aninstance of a COM object that constitutes the XML DOM representation of the dataisland contents. The following pseudocode, written in JScript, illustrates this point; thevariable xmldoc is an XMLDOMDocument object.// Extract the data island contents// xmldoc is the ID of the tagvar xmldata = document.all("xmldoc").innerHTML;// Instantiate MSXML499