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Web applications have historically been less rich and responsive than desktop
applications. End users don’t necessarily understand the details of how an
application works, but they know that interacting with a website in the browser
is distinctly different from using an application installed locally. When a
development team tackles a new project, one of the first questions they are
faced with is whether end users can accept the limitations of web development
or whether they need to require a client desktop application to be installed.
Web applications are accessible from just about any browser, just about
anywhere, but they are limited by what you can do with markup and script code
running in the browser.
Desktop applications, also called fat client applications, require that the user
perform an installation on their machine, but let developers leverage the
advanced mouse and graphics capabilities of the operating system that would be
extremely difficult to implement in a web browser, and also take advantage of
the user’s machine for tasks such as offline storage. Conversely, web
applications can be updated just by changing what is running on the server, and
site visitors get the latest version instantaneously. However, it’s much more
difficult to update a desktop application, because you’d have to get users to
perform yet another installation or else ensure that the application has been
coded to include a clever system for doing updates automatically.
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Book Excerpt: Developing Next-Generation Web Applications
Chapter Contents
This excerpt from
Professional ASP.NET 2.0 AJAX by Matt Gibbs, Dan Wahlin, is
printed with
permission from Wrox Publication.
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Web applications are said to use a zero-deployment model, but desktop
applications use a heavy deployment and configuration model. The choice is
often characterized as a tradeoff between rich and reach: Desktop applications
generally offer a richer user experience than what could be offered in the
browser, but with a web application you are able to reach users anywhere on any
OS with almost no extra effort. Further, many companies have restrictive
policies in place regarding what software can be installed on employees’
machines, and they often don’t allow employees to have administrative access
that is required to install new applications, so web applications will be the
only viable option in many situations.
Bringing Richness to Web Applications
Years ago, having a web presence was a distinguishing factor for companies. That
is no longer the case. Now just having a web presence is no longer enough.
Companies are distinguishing themselves further through web applications that
react intuitively to customer actions and anticipate user input. This book
shows you how ASP.NET AJAX addresses specific web development challenges and
paves the way for taking your website to another level of user experience. In
this chapter, I discuss the need for richer frameworks in web application
development. I talk about the key pieces of the ASP.NET AJAX platform and
highlight some other options.
The fundamental set of technologies that enable the next generation of web
applications are not new. Online news articles and blogs point to Google,
Flickr, and several other services as prime examples of leveraging these
technologies in unique ways. The applications have some unique features, but in
reality, the underlying technologies have been around and in use for nearly a
decade. Take a look at how Microsoft Exchange Server provided rich access to
email from a web browser in the Outlook Web Access application, and you can see
that the concept of ubiquitous access from a browser while leveraging a common
set of browser features for a rich user experience has been around and in
practice for years. Users get a remarkably full-featured application with no
local installation and are able to access e-mail from virtually any machine.
The technologies in use for building rich applications are generally referred to
as AJAX (Asynchronous JavaScript and XML). While the acronym is nice, it
doesn’t do much to explain what is actually happening. Instead of building a
web application to be just a series of page views and post backs, developers
are using JavaScript to communicate asynchronously with the web server and
update parts of the page dynamically. This means that the web page can
dynamically adapt its appearance as the user interacts with it, and it can even
post or fetch data to or from the web server in the background. Gone are the
days of the ugly post back, which clears the user’s screen and breaks his
concentration! Instead, we need to post back now only if we want to change to a
different web page.
The AJAX acronym refers to XML as the data format being exchanged between client
and server, but in reality, applications are being built that retrieve simple
pieces of text, XML, and JSON (JavaScript Object Notation) (which I discuss in
more detail in Chapter 4). Part of the AJAX appeal isn’t even covered by the
acronym: In addition to communicating with the server without blocking,
developers are leveraging Dynamic HTML (DHTML) and Cascading Style Sheets (CSS)
to create truly amazing user interfaces. JavaScript code running on the client
communicates asynchronously with the server and then uses DHTML to dynamically
modify the page, which supports rich animations, transitions, and updates to
the content while the user continues interacting with the page. In many cases,
users won’t even realize they are using a web application!
More Related links
Answer - ASP.NET Ajax Framework is used for implementing the
Ajax functionality......
Answer - Back functionality cannot work because the dynamic
pages don’t register themselves to the browsers history engine..........
With ASP.NET 2.0, Microsoft introduces a new feature known as validation groups,
which enables you to create different groups of validation controls and assign
them to input controls, such as text boxes. You can assign a validation group
to a collection of input controls if you want to validate the collection of
input controls on the same criteria............
One of the neat features of ASP.NET 2.0 is themes, which enable you to define
the appearance of a set of controls once and apply the appearance to your
entire web application............
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