MSDN Magazine - November 2008 - (Page 31)

DINO ESPOSITO Cutting EdgE Browser Interoperability In Silverlight 2 You can use Silverlight 2 to build full-page Windows Presentation Foundation (WPF)-like Web applications or to enrich HTML-based pages with additional features such as animations, advertising, and specific applets. The browser doesn’t directly process the eXtensible Application Markup Language (XAML) content that makes up a Silverlight application. Instead, within the HTML page, an tag points to the Silverlight 2 plug-in and has among its parameters the URL to download any necessary XAML resources. The bottom line is that there’s always an HTML page wrapped around a Silverlight plug-in, even though you often can’t see it because the Silverlight application is configured to run in full-screen mode. In addition, the content hosted by the Silverlight plug-in is not isolated from the surrounding page in a same-site situation. When the Silverlight content comes from a different domain than the hosting HTML page, then it is indeed isolated from the page. Silverlight comes with a browser interoperability layer that allows managed code to access the document object model (DOM) of the underlying page and register managed handlers for pagelevel events. At the same time, any JavaScript code running in the page can gain access to the XAML content of the plug-in and even make modifications. Finally, JavaScript code running in the page can also invoke managed functions as long as these functions are exposed properly. This month I’ll discuss the browser interoperability layer of Silverlight 2 and the ways you can take advantage of it in your applications. Figure 1 lists the properties you can set to configure the Silverlight plug-in. The properties in Figure 1 refer to the Silverlight ASP.NET control that executes on the server side and spits out an tag that may have differently named parameters or no equivalent parameters. For the purposes of this column, you should pay a lot of attention to the HtmlAccess property. (Note that this part of the Silverlight SDK changed a bit in the transition from Beta 1 to Beta 2.) The HtmlAccess property indicates the level of access to the underlying page DOM that the Silverlight application is allowed. The A Silverlight plug-in always has an HTML page wrapped around it. property accepts values from the HtmlAccess enumerated type. Values are listed in Figure 2. Obviously, Enabled and Disabled are self-explanatory. The default setting is SameDomain, which doesn’t inject any script in the page’s markup. Note that a Silverlight application can be hosted in a page that is, in turn, hosted within a frame outside of its native domain. In this case, the Silverlight managed code is able to access the DOM of the host page in a cross-domain manner. Browsers have their own barriers to prevent cross-domain scripting, but they can’t do much to stop the managed code within the Silverlight plug-in. Authors of Silverlight pages use HtmlAccess to control cross-domain access. Once access to the underlying page DOM has been granted, a Silverlight application can use the members on the static class HtmlPage to accomplish its own tasks. Figure 3 lists properties and methods of the HtmlPage class. This column is based on a prerelease version of Silverlight 2. All information is subject to change. Code download available at msdn.microsoft.com/magazine/cc135911. Send your questions and comments for Dino to cutting@microsoft.com. November 2008 31 Configuring the Silverlight Control As mentioned, the Silverlight plug-in is invoked through an tag. However, this tag can be created for you by an ASP.NET control in ASP.NET pages. When you create a sample Silverlight application in Visual Studio 2008, the following markup for the Silverlight server control is automatically inserted in the test page: Accessing the DOM from Silverlight The MinimumVersion attribute indicates the minimum version of the Silverlight runtime that is required to run the application specified in the Source attribute. Width and Height define the size of the Silverlight window with respect to the host page. As you can see, by default the Silverlight plug-in is configured to run in full-size mode. http://msdn.microsoft.com/magazine/cc135911

Table of Contents Feed for the Digital Edition of MSDN Magazine - November 2008

Contents MSDN Magazine - November 2008 Toolbox CLR Inside Out Data Points Cutting Edge Security Briefs Test Your Security IQ Agile SDL Access Control Utility Spotlight RIA Test Run Wicked Code Foundations Team System End Bracket

MSDN Magazine - November 2008

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