MSDN Magazine - January 2009 - (Page 31)

DINO ESPOSITO Cutting EdgE Managing Dynamic Content Delivery In Silverlight, Part 1 Users of any rich Internet application (RIA) have valid concerns about security and download size. Silverlight applications are backed by a subset of the full Microsoft .NET Framework and, as such, have the potential to take harmful actions against the local user machine. For this reason, the Silverlight team developed a new security model that makes it impossible for applications to call into any security-critical class in the Core CLR (the Silverlight edition of the .NET Framework). You can read more about the Silverlight security model at msdn.microsoft.com/magazine/cc721609 and more about building Silverlight apps in “Get Started Building a Deeper Experience across the Web” at msdn.microsoft.com/magazine/cc163404. Downloading the Silverlight plug-in is not really an issue, as it takes just a few seconds and is an operation that you run only once. But what about the size of downloaded applications? In this month’s column, I’ll tackle the question of Silverlight application downloads. First, I’ll illustrate how you can generate XAML dynamically. Next, I’ll discuss how to enable application features dynamically on a strictly per-user request basis. Some applicationspecific features that are heavy to implement with the main stream of code can then be implemented separately and, more important, downloaded separately and still be easily integrated with the primary user interface. Figure 1 An HTTP Handler that Returns XAML using System; using System.Web; public class XamlGenHandler : IHttpHandler { public void ProcessRequest (HttpContext context) { // Prevent caching of the response context.Response.Expires = -1; // Set the type of data we're returning context.Response.ContentType = "text/xaml"; // Create some XAML and return it down the wire context.Response.Write(" " + " XAML content " + " [generated " + DateTime.Now.ToLongTimeString() + "] " + " "); } public bool IsReusable { get {return true;} } } The Size of Silverlight Applications Once a user has installed the Silverlight plug-in, he has in place all system assemblies that a Silverlight application may require. This means that the download is limited to the assembly that contains the application, plus any referenced custom assemblies. In the end, the size of the application download is often in the tens of kilobytes. Note that this estimation applies to the RTM version of Silverlight 2 and to code compiled in release mode. Of course, the application might have a much larger footprint, especially if it contains long algorithms, graphic and media content, or animations. To deal with large applications where the download time becomes a problem, you have two main options. One is to stream the Silverlight content as discussed at silverlight.live.com. The other option is to split the application into independent pieces that can be downloaded separately and on demand. in processes the code to produce the user interface and support any coded behavior or effects. The XAML can be pointed to directly via a URL if it is all that you want to be downloaded; otherwise, you can reference a Silverlight package through the XAP extension. A XAP package contains a manifest and one or more assemblies. One of the assemblies contains the entry point of the application; other assemblies are just referenced assemblies. The XAML for the user interface is stored in the resources of the entry point assembly. A XAP package is created by the Visual Studio 2008 extension for Silverlight 2 when you create and build the project. XAML and XAP streams are all that the Silverlight plug-in knows how to handle. To download such content, though, you don’t necessarily have to point the plug-in to a physical XAML or XAP resource on the server. You can, for instance, point the plug-in to a URL that can return dynamically generated XAML or XAP content. Send your questions and comments for Dino to cutting@microsoft.com. Code download at code.msdn.microsoft.com/mag200901cutting. January 2009 31 Dynamically Generated XAML The Silverlight plug-in is essentially designed to display XAML content. If the XAML comes with some codebehind, then the plug- http://msdn.microsoft.com/magazine/cc721609 http://msdn.microsoft.com/magazine/cc163404 http://silverlight.live.com http://code.msdn.microsoft.com/mag200901cutting

Table of Contents Feed for the Digital Edition of MSDN Magazine - January 2009

Toolbox CLR Inside Out Basic Instincts Cutting Edge Test Run First Look� Geneva Framework Silverlight Windows Mobile Service Station Security Briefs Extreme ASP.NET Foundations .NET Matters { End Bracket }

MSDN Magazine - January 2009

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