c# thoughtworks qrcode More INfo in Visual C#

Painting QR Code in Visual C# More INfo

For details about all the practice test options available, see the How to Use the Practice Tests section in this book s Introduction.

ich Internet applications (RIAs) are becoming the norm on the web. Users expect a high degree of interactivity when working with modern websites the same interactivity that was once only expected of applications running on the desktop. This includes functionality such as modal dialog boxes and pop-up windows, partial screen (or page) updates, controls that dynamically collapse or resize on a page, application progress indicators, and much more. Microsoft ASP.NET includes tools for building web applications that provide this level of richness. These tools include controls for handling client-based interactivity, an extensive library for working with client-side JavaScript, a programming model for creating your own JavaScript enabled controls, and newly added support for the jQuery library. This chapter covers these scenarios and shows you how to enrich your users experiences with your websites.

Exam objectives in this chapter:

Implement ASP.NET AJAX. Add dynamic features to a page by using JavaScript. Handle JavaScript events. Alter a page dynamically by manipulating the DOM. Implement AJAX by using jQuery.

Lessons in this chapter:

455 471

To complete the lessons in this chapter, you should be familiar with developing applications with Microsoft Visual Studio 2010 by using Microsoft Visual Basic or Microsoft Visual C#. In addition, you should be comfortable with all of the following:

The Visual Studio 2010 Integrated Development Environment (IDE) Using Hypertext Markup Language (HTML) and client-side scripting Creating ASP.NET websites and forms Adding web server controls to a webpage

am fortunate enough to have been around when building web applications first took off. The early applications we built were nothing more than hyperlinked HTML

and some images. Soon we added server-side script and database connectivity to enable more meaningful scenarios. The power of having a server-based, near-zero deployment, ubiquitous, crossplatform application environment has been (and still is) the driving force that pushes us to build web applications. There has always been, however, a major gap in the richness of the user interface (UI) between a desktop application accessing the web and a web browser. We ve seen many attempts to close this gap, including Java, Microsoft ActiveX, ActiveX Documents, Dynamic Hypertext Markup Language (DHTML), and others. It remains to be seen whether this gap will ever really be closed. However, Asynchronous JavaScript and XML (AJAX) and jQuery both provide a nice compromise between a rich client and a web-only application. These technologies extend what is capable on the client without breaking the paradigm of a web application. AJAX is rooted in the web and, like its counterparts HTML and DHTML, it is standards driven, cross platform, and ubiquitous. This makes it a great choice for adding client interactivity to applications that must remain true to the concept of a website.

Much of what makes Web 2.0 applications so appealing to users is provided by AJAX. This technology enables increased user interactivity when an application running in a browser is used, because the application requires fewer page refreshes. The result is a better user experience on the web. AJAX is a platform-independent technology that works with web applications running in Windows Internet Explorer, Firefox, Safari, and other browsers. It is an ECMAScript-compliant technology. (ECMAScript is the foundational language from which JavaScript and JScript are derived see http://en.wikipedia.org/wiki/ECMAScript.) This makes AJAX a logical choice for providing a richer UI for browser-based, cross-platform web applications. You can add AJAX to any web application. Like other web standards such as HTML, it is not specific to ASP.NET. However, ASP.NET does provide many tools that make building AJAXenabled webpages easier. These include controls to manage partial-page updates, a code library that enables object-oriented development on the client with JavaScript, the ability to call web services from client code, the ability to create your own AJAX-enabled controls, and more. This lesson covers building interactive web forms by using the AJAX controls built into ASP.NET 4. The JavaScript object library and building AJAX-enabled controls are covered in Lesson 2 of this chapter.

After this lesson, you will be able to:

Understand and use the AJAX Extensions controls built into ASP.NET. Create a web form that performs partial-page updates to the server (without a full-page refresh). Display the progress of a request that is being processed on the server. Periodically update portions of a webpage based on a time interval.