Well, it’s been a while since I first posted on this, but the feedback was incredible, and I got some great suggestions.  As a result, I’ve updated the Activity control and (finally) have a running sample on the web!  The fundamental idea of the control has remained the same, as well as the mechanisms by which it can work.  It’s still a prototype, but a very useful one at that!

To see the Activity control in action, take a look here: Activity Control Demo

The demo requires the Silverlight 3 beta to be installed on your machine, which can be found here: http://silverlight.net/getstarted/silverlight3/default.aspx

The demo application shows two examples of using the Activity control to display async/background activity (click the images for deep-links into the Silverlight application):

  • With .NET RIA Services and the DomainDataSource, the Activity control uses element-to-element binding to indicate to the user that data is being loaded or submitted.  The demo page is running live on my server using the Northwind sample database.  Those of you who think you can play some dirty tricks by overwriting the data on my server (yes, I provided insert/update/delete functionality) – any attempts to do so will be quickly foiled, since the server will accept the requests, but ignore them! ;)

.NET RIA Services with the Activity Control

  • Any background activity might warrant using the activity control.  The second example I’ve provided uses the activity control while I use a simple statistical method of approximating PI (yes, very geeky).  It takes millions of iterations to get a mediocre approximation of PI (I know, I’m not using an efficient method, but it does do a lot of work!).  Here, I’ve augmented the Activity control to allow the work to be stopped/cancelled:

Calculating PI with background activity


So by now I’m sure you’re asking: “What’s changed?”  Well, let me tell you!

  • Thanks to feedback from a variety of folks, I’ve removed the all-encompassing template that included the pop-up window.  That’s now baked into the control template.  If you’d like to change it, you can use the Blend 3 Preview to re-template the control.  In its place, I’ve added:
    • A style for the progress bar.  If you’d like to hide it, use a style to collapse the progress bar.
    • A means for setting “ActiveContent”.  The Activity control works sort of like a HeaderedContentControl.  You now have ActiveContent and ActiveContentTemplate, which allow you to define in XAML what should appear above the progress bar.  You can put any content you like here, and it’s how I added the cancel button in my PI calculation example.  This is also great because it allows you to easily change the text from “Loading…” to whatever you prefer simply be setting the ActiveContent property to the string of your choice!
  • The default template for the ActivityControl now sets IsHitTestVisible and IsEnabled to false on its content immediately when IsActive becomes true.  In my old prototype, this only happened when the Activity UI became visible, which meant users could continue to interact with the content while it was busy – a potentially dangerous combination if the user’s interactions can be overriden by the asynchronous work (such as editing values in a DataGrid when the data is being reloaded).  This was from a suggestion by Luke Tigaris in the comments on my last post.  Let me know what you think!
  • You can now call ResetActivity() on the control to force it to honor the visibility of the control immediately rather than enforcing the display delay and minimum display time.  This way, if a user cancels the background work, you can force the Activity UI to be hidden immediately.


Anyhoo, let me know what you think of the changes!  I’ve gotten lots of great feedback on the control so far, and I’m sure folks will come up with more as time goes on.

For both of these, you’ll need the Silverlight 3 Beta.  The Demo application is built using .NET RIA Services.

P.S.  Big thanks again to Corrina for providing the beautiful theme I used in my application.

P.P.S.  Isn’t navigation and deep-linking in the Silverlight 3 Beta cool?  That’s how I made those images link directly to the corresponding pages of my demo application.  I may post more on this in the future.  In the meantime, take a look at the code to see just how little it took to accomplish that! (hint: MainPage.xaml in the Silverlight Navigation Application project template that’s included with the Silverlight 3 Beta Tools for Visual Studio has pretty much everything that’s required)

Update 9/14/2009 – I’ve made a small update to the Activity control to fix a performance issue.  You can find it here.