MSDN Magazine - October 2007 - (Page 50)

layout,data binding,and styling.The JavaScript environment has no support for any of them,except for some styling support through CSS. In addition, JavaScript is an interpreted language where, for example, intensive programming often results in memory issues due to subtle browser bugs and poor programming. Consider a relatively common and simple scenario—paging a grid of data. A grid is ultimately a rather complex table that the browser has to parse and render for each request.It’s More powerful tools are hard for a user to measure needed on the client in order the cost of this rendering operation the ﬁrst time the to make creating realistic page is served since it is inuser interfaces effective. corporated in the overall page download. But once an AJAX postback request is made for a new grid page, the cost of updating the browser’s window is immediately evident.The browser receives a JSON string that contains a collection of objects and must turn that collection into a new table.A big HTML string has to be built on the client, composing text in some memory buffer. The same string, if correct, then has to be rendered graphically. When such intensive operations are performed,you may notice a less than ideal response time. For scenarios like this, above average JavaScript and DHTML skills are required in order to come up with effective solutions. An alternative approach is to pre-generate some of the markup on the server.In this way,the remote service doesn’t just return data but also incorporates markup information.On the server,the markup is built through compiled code,it can be more easily debugged and tested, and you have access to more powerful programming tools for adding accessibility features. On the other hand, more data travels over the wire (but keep in mind that the amount of data is still much less than with regular ASP.NET postbacks). The bottom line is that more powerful tools are needed on the client in order to make creating realistic user interfaces effective from both the performance and development perspective. Good, thorough libraries of widgets and controls are essential to any developer. But even the best, most optimized libraries can’t do much to counter the inherent limitation of an interpreted language,such as JavaScript.Perhaps Silverlight,a Microsoft cross-platform browser plug-in that incorporates a subset of the Windows® Presentation Foundation (WPF) framework,will eventually offer the client-side environment that Web developers will desire for their next generation of Web and AJAX applications. But Silverlight is an external plug-in; it requires a separate download, and it is still maturing. Version 1.0 has just been released,but more sophisticated features are needed in order to use it to build the presentation layer of realworld Web applications. What It All Means Partial rendering is the easiest approach to AJAX. It is particularly well suited for addingAJAX capabilities to legacy applications that you don’t have the time,budget,or desire to redesign.From an architectural standpoint, partial rendering is a smart extension to today’s ASP.NET that preserves the same application model and underlying engine. A pure AJAX architecture is based on client and server being loosely coupled—essentially two separate worlds connected over the HTTP wire with JSON exchanging messages. In a pure AJAX architecture, you have a service-based back end and a JavaScript-powered front end.The burden of building an effective HTML UI is entirely up to you or the control library you choose. This decoupling, however, will allow for emerging technologies, such as Silverlight, to continue enabling Web developers to create more interactive user interfaces without being constrained by the server platform. Code download available at msdn.microsoft.com/msdnmag/code07.aspx. Send your questions and comments for Dino to cutting@microsoft.com. Dino Esposito is a mentor at Solid Quality Learning and the author of the upcoming Programming ASP.NET 3.5 Core Reference (Microsoft Press, 2007). Based in Italy, Dino is a frequent speaker at industry events worldwide. You can visit his blog at weblogs.asp.net/despos. 50 msdnmagazine Cutting Edge http://ASP.NET http://msdn.microsoft.com/msdnmag/code07.aspx http://www.windowscontrols.com http://weblogs.asp.net/despos

Table of Contents Feed for the Digital Edition of MSDN Magazine - October 2007

Cover Contents Toolbox CLR Inside Out Basic Instincts Data Points Cutting Edge Pooled Threads WPF Threads Parallel Linq Parallel Performance Mobile Apps Test Run Foundations Windows with C++ Netting C++ .NET Matters { End Bracket } Net Nuptials

MSDN Magazine - October 2007

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