asp:review
PowerWEB LiveControls for ASP.NET
There s No Comparison
By Steve C. Orr
You may have heard some of the buzz lately about client-side callback technologies such as AJAX and XMLHTTP. These techniques are an efficient way to keep Web page content current without requiring the page to continually post back. Postbacks are slow and ugly, causing all page content to post back to the server, which must then re-render the entire page and send the whole thing back to the browser, which then redraws the entire page from scratch.
Conversely, lightweight client-side technologies like AJAX and XMLHTTP send minimal amounts of data between the client and the server, and allow the Web browser to only redraw the relevant controls, while leaving the rest of the page untouched. This can create a much more graceful and enjoyable Web surfing experience for your users.
PowerWEB LiveControls by Dart Communications uses such lightweight techniques to extend the standard ASP.NET Web controls and make them far more efficient. It then goes above and beyond with new controls that most Web developers wish they had.
Free Test Drive
Developer licenses are free, so go ahead and download the demo and try it out risk-free. You only need to pay if you like the product enough to deploy it to your live site. The installation is quick and easy. The set-up program goes beyond most, offering to integrate its comprehensive help documentation with Visual Studio and to automatically create the virtual directories needed to run the sample applications (see Figure 1). It would have been nice if the installation program automatically added the controls to my Visual Studio.NET toolbox, but adding the controls manually only took a minute or two.
Figure 1: The user-friendly
installation offers to create the sample application virtual directories
automatically so you can get started quickly.
The sample applications are relevant, useful, and easy to understand. The sample code (provided in both C# and VB.NET) is well written and suitably commented. Thanks to the thorough set-up program, the sample applications ran immediately with no tinkering necessary.
The controls are intuitive, with almost no learning curve necessary. In my first experiment I dropped a LiveButton control and a LiveLabel control onto a form. In the LiveButton s server-side Click event I added a standard line of code to update the LiveLabel s Text property with the current date/time:
LiveLabel1.Text = Date.Now.ToString
I then ran the application; I clicked the button and saw the label immediately update with the server s current time without an ugly postback. It s as simple as that the controls just work. You write normal code inside normal server-side events and, generally, everything works just as you d expect from standard Web controls, except all the communication happens smoothly behind the scenes with client-side callbacks.
When the server events are fired you can expect all forms of state to be fully hydrated, including ViewState, Session, Application state, etc. As far as your server-side code need be concerned, it can function as if the callback were a normal postback. However, keep in mind that if you try to update a control other than a PowerWEB LiveControl during a callback, that control s user interface won t be updated by default because the page is not being re-rendered. (If you really want to be able to update a non-PowerWEB control, there are a couple controls provided in the suite that can wrap other Web controls to provide them with the benefits of client-side callbacks.)
A Full Suite of Feature-rich Controls
There are more than 20 controls included in the LiveControls suite. Many of them are simple extensions of the standard ASP.NET Web controls, and then there are some extras that really sell the suite as a whole.
In addition to the LiveButton and LiveLabel controls mentioned previously, there are also LiveImage (see Figure 2) and LiveImageButton controls that can update their own images dynamically. This is a great way to provide a slick slideshow for users, but the enhancements don t stop there. Their interactivity approaches that of a Windows Forms application. The LiveImage control (as well as most of the other controls) have events such as MouseDown, MouseUp, MouseLeave, DoubleClick, and other kinds of server-side events that Web developers have been deprived of for far too long. The events are fired quickly and efficiently, so Web page response is snappy.
Figure 2: The LiveImage control can
update itself via client-side callbacks to provide slick slideshows that don t
interfere with the user s Back button functionality.
There are other familiar controls that have equally impressive features, such as the LiveCheckBox, LiveCheckBoxList, LiveRadioButton, LiveRadioButtonList, LiveDropDownList, LiveListBox, LiveHyperLink, LiveLinkButton, LivePanel, etc.
The LiveTextBox control can stream keystrokes back to the server as they happen, allowing you to make a back-up copy of the user s data entry in case of a browser crash or other unfortunate incident that might otherwise cause data loss.
The LiveDataGrid control allows a grid to page and sort itself without refreshing the rest of the page. It also permits users to select, delete, and edit records just as fluidly.
All of the controls in the suite share some common properties, such as the IsLive and EnableCallback properties that permit the controls to do standard postbacks in case you should ever yearn for the old days. They also provide a WaitMessage property that can display a message in cases where a callback requires unusually intensive processing. The WaitElementID property can specify a particular control to display that message. The UpdateAll property allows other LiveControls to update themselves too, whenever a callback occurs from any control. When set to False, only the form element that caused the callback will participate in the callback. There are also properties that allow callback errors to be handled in a variety of customized ways, and an extended Font object that permits controls to change their appearance dynamically.
Create Unique Solutions with Unique Controls
All the controls mentioned previously extend the standard ASP.NET Web controls in useful and efficient ways, but what really sells the suite are the extra controls that can t be compared to any of those within the stock Visual Studio.NET Web controls toolbox.
The LiveMessageBox control allows messages to be displayed dynamically, including alerts, confirmations, and input boxes. The LiveMessageBox_Response event allows the developer to collect and process the user s response.
The LiveTimer control (see Figure 3) acts very much like a Windows Forms timer control. After the specified number of milliseconds, a Timer event is sent to the server, allowing processing to happen on a frequent and reliable basis. While I expect the timer can t be especially accurate when set to a small number of milliseconds, the tiny and efficient callbacks can happen far more quickly (and therefore far more often) than standard page postbacks ever could. One of the sample projects demonstrates how this control can be used to create a progress bar that continually updates the status of an ongoing server operation.
Figure 3: The LiveTimer control can
call back to the server at regular intervals so status bars and other page
elements can be updated in real time. The LiveSound control can be used to
trigger audible alarms in the case of important events that demand attention.
The LiveSound control allows audio to be played from within a Web page. These sounds can be played dynamically in response to user actions or events occurring on the server.
The LiveWrapper and LiveCallback controls provide a way to enhance other (non-PowerWEB) controls to participate in callbacks too, so you can use callbacks easily with virtually any Web control in existence.
Competition from ASP.NET 2.0?
If you are developing ASP.NET 1.x and you want to bless your users with the power of client-side callbacks, the decision to use PowerWEB LiveControls for ASP.NET is a no-brainer. Without this powerful cross-browser-compatible control suite, client-side callbacks in ASP.NET 1.x are too complex to be feasible for most Web applications. However, with these controls it becomes as simple as the code you already write every day.
If you read my November 2005 ControlFreak article about the new client-side callback capabilities of ASP.NET 2.0, then you know client-side callbacks are becoming more feasible with standard Web controls than they used to be (see ASP.NET 2.0 Callbacks). Of these new client-side callback capabilities, they re most easily used with the new TreeView and GridView controls because callback features have been specifically built into these two controls. As for the other controls of ASP.NET 2.0, well, it s easier than it used to be to power them up with client-side callbacks, but that s not saying much. It still takes a moderate amount of slightly convoluted code to make it happen. I wish all the primary controls of ASP.NET 2.0 had callback technology built into them like the TreeView and GridView. Coincidentally, that s exactly what PowerWEB LiveControls provides, plus some very enticing new controls, as well. So when it comes to comparing PowerWEB LiveControls to the new client-side callback technology of ASP.NET 2.0, there s really no competition.
Development licenses are free, a single-server license is US$499, and prices decrease as you buy more server licenses. But when you think about it, can you really put a price on happy users and effective developers? When you buy these high-quality controls you re purchasing a superior user experience for your Web sites along with turbocharged development efficiency.
Steve C. Orr is an MCSD and a Microsoft MVP in ASP.NET. He s an independent consultant who develops software solutions for many leading companies in the Seattle area. When he s not busy designing software systems or writing about them, he can often be found loitering at local user groups and habitually lurking in the ASP.NET newsgroup. Find out more about him at http://SteveOrr.net or e-mail him at mailto:[email protected].
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Web Site: http://dart.com/powerweb/livecontrols.asp
Price: US$499
