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

var parser = new ActiveXObject("Microsoft.XMLDOM");// Parse the contents of the data island and makes// it available as a XML DOM object. The object is given// the same name as the tag's IDvar xmldoc = parser.loadXML(xmldata);If your final goal is consuming the data island within the body of a managed control,there is no need to pass through a COM-based intermediate representation of the XMLdata. In this case, in fact, the parser that will actually process the data is the .NETFramework XML reader. The reader needs only a string of XML data, not a COMobject. On the other hand, whenever you use the tag, Internet Explorerautomatically creates the XMLDOMDocument object. So if the final destination of thedata island is a Windows Forms control, you might want to speed things a little bit bynot using the tag, which will produce a useless COM XML DOM object. Using ahidden field offers the same functionality at a lower price. But keep in mind that thisoption is valid only if you plan to consume the data island contents through embeddedmanaged code.The Role of Script CodeTo establish a connection between the host environment and the managed control, youmust use script code—Javascript in particular. For this reason, while you're designingthe interface of the managed control, don't forget what the actual callers of thosemethods will be. A Javascript client has different capabilities than a .NET Frameworkclient, so you should keep the signature of public methods as simple as possible andavoid using arrays and other complex and user-defined types.In the dataisland.aspx sample code, the connection between the data island and themanaged control is made through the Load method. The Load method accepts a simplestring, which results in a signature that the Javascript code can easily match, as shownhere:// At this point, Internet Explorer has already created// the XMLDOMDocument. You can retrieve the content of the// data island either through the XMLDocument object or// the innerHTML property.var data = xmldoc.XMLDocument.xml;// Pass the data island content to the managed controlvar listView = document.all("grid");listView.Load(data);Avoiding Problems with Submit ButtonsWhile developing the sample ASP.NET page to test the DataListView object, I ran intoan interesting snag. I originally used the tag to insert a button to load thedata island into the control. As a result, the data island was correctly read and thecontrol filled, but a moment later the page refreshed, and the control lost its state andwas displayed as empty. What happened? The reason for this strange behavior is thatthe tag always generates a submit button, as shown here:500