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Silverlight RIA

Today we are happy to be able to announce the availability of some Silverlight 4 book content. For existing Silverlight developers looking to get up to speed quickly with the features we are releasing the Silverlight 4 Overview. This is a little over 50 pages of content covering the new Silverlight 4 features.  For the rest of this week using code SL4DaveBlog at checkout you can get the new Silverlight 4 content for only $5 almost half off the normal price.  More details on the book site

For developers that are new to Silverlight but are comfortable with .NET we are releasing a preview of Silverlight 4 Jumpstart. Silverlight 4 Jumpstart content builds on the success of the Silverlight 3 Jumpstart book to offer content focused at the business .NET developer.

Both of these offerings are available today and will continue to evolve with the Silverlight 4 release. These are delivered in an electronic format (PDF) and will continue to be updated with more current releases of Silverlight 4.


The following is an excerpt from the Silverlight 4 Overview chapter that is available as part of Silverlight 4 Jumpstart Preview book or as a standalone chapter from The full overview chapter covers all the major new features of Silverlight 4 to help you get up to speed quickly.

Microsoft has fast tracked Silverlight to be a strong competitor in the global RIA space and squarely positioned itself against competitors like Adobe, Google and Yahoo for production of the finest RIA toolset. The initial battleground was video, but we are now seeing Silverlight has strong potential for building business applications as well. We have tried through the previous chapters to streamline your learning of the current version of Silverlight by focusing on the key areas a business developer needs to know. Now it’s time to talk about the future and what the road ahead looks like for Silverlight.

It had only been about nine months since Silverlight 2 was released in October 2008 that Silverlight 3 hit the street in July 2009. Then, just four months after the release of Silverlight 3 Microsoft released Silverlight 4 Beta at its Professional Developer Conference in November 2009. Each of these releases build on the prior one to add new features while at the same time keeping compatibility to support this fast pace of innovation.

If I had to pick a single theme for the main items that are part of Silverlight 4 I would have to choose “You Asked, Microsoft built it”. I say that because many of the items like Printing or Web Camera/Microphone support for example were some of the highest user prioritized features. You can check that out for yourself at and while you’re there add or vote on a couple of your requests.

Silverlight 4 is also a major deal because it’s the first release of Silverlight to support .NET 4 CLR (Common Language Runtime). This gives developers access to the latest runtime features that are added to CLR4 including things like dynamic object support.

In addition to the core Silverlight 4 Beta, Microsoft also released corresponding updates to the other tools and products used with Silverlight. The tools for working with Silverlight from within Visual Studio were updated to support the Silverlight 4 Beta. This includes increased designer support to make it easier to develop Silverlight applications without having to leave Visual Studio for a separate tool. A new version of the Silverlight Toolkit was also released that goes along with the Silverlight 4 update. An update was also released for .NET RIA Services which has now been renamed as WCF RIA Services to reflect the fact that it now rides on top of WCF. This is an evolution of the prior .NET RIA Services releases and positions it to leverage WCF as a foundation to build on going forward. In addition to the WCF change a number of additional features such as improved inheritance support were added to WCF RIA Services in this release. Finally, a preview release of Blend for .NET 4 was released to allow it to work with Silverlight 4.
In the rest of this chapter we are going to preview some of these features that you will see in the Silverlight 4 Beta release.

Web Camera / Microphone Support

Silverlight 4 now allows developers to access to the raw audio and video streams on the local machine from applications running both in and out of the browser. Using these capabilities developers can write applications including capture and collaboration using audio and video. This is built-in to the core runtime and no other special downloads are required on each machine. When the audio or video is accessed for the first time by the application the user will be prompted to approve the request. This ensures that audio and video is never accessed without the user’s knowledge preventing applications that capture silently in the background. The following is an example of the prompt the user sees when the application requests access to the devices.


You will notice in the above image the site name is displayed. This is another safeguard to ensure the user knows which site is requesting access to the devices. Access is granted to just this application and only for this session of the application. Currently there is no option to persist the user’s approval to avoid re-prompting each time the application is run. Additionally, it’s all or nothing; you don’t get to choose video or microphone. It’s a combined approval.

Users with multiple devices can select the devices they want to be the default devices using the properties on the Silverlight plug-in. This can be selected by right-clicking on a Silverlight application and going to the Webcam/Mic tab.

The following is an example of what you will see on that tab.choosedefaultmic

Developers can get access to the chosen devices using the CaptureDeviceConfiguration class. Using this class you can call the GetDefaultAudioCaptureDevice or GetDefaultVideoCaptureDevice methods to retrieve the users selected defaults. The class also has GetAvailableAudioCaptureDevices and GetAvailableVideoCaptureDevices methods that allow you to enumerate the available devices if you want more control of choosing a device besides the default.

Prior to using the devices you must request access to the device by calling the RequestDeviceAccess() method from the CaptureDeviceConfiguration class. When this method is called it is responsible for showing the user approval dialog we saw earlier. This method must be called from a user initiated event handler like the event handler for a button click event. If you call it at other times it will either not do anything or produce an error. Using the AllowedDeviceAccess property you can query if access has already been granted to the device.

The quickest way to get started using the video is to attach the capture from the device to a VideoBrush and then use the brush to paint the background of a border. The following XAML sets up the button to trigger the capture and a border that we will paint with a video brush.


<Button x:Name="btnStartvideo" Click="btnStartvideo_Click"

Content="Start Video"></Button>

<Border x:Name="borderVideo" Height="200" Width="200"></Border>


Next, the following private method TurnOnVideo method is called from the handler for the click event on the button. This satisfies the requirement to be user initiated.

private void TurnOnVideo()


VideoCaptureDevice videoCap =


AudioCaptureDevice audioCap =


CaptureSource capsource = new CaptureSource();

capsource.AudioCaptureDevice = audioCap;

capsource.VideoCaptureDevice = videoCap;

if (CaptureDeviceConfiguration.AllowedDeviceAccess

|| CaptureDeviceConfiguration.RequestDeviceAccess())



VideoBrush vidBrush = new VideoBrush();


borderVideo.Background = vidBrush;



As you can see in the code above, default audio and video devices are retrieved and assigned to a CaptureSource. Access to the devices is then checked and requested if not already approved.

If access is granted the Start() method on the CaptureSource is invoked to begin capturing audio and video. Finally, the VideoBrush source is set to the CaptureSource instance and the background on the border is set to the VideoBrush.

Overtime we will probably see some very interesting applications of the audio and video support. One example that we put together was using it with Microsoft Dynamics CRM. In this example application a membership application was simulated that associated members with pictures and stored the pictures in a database. Think of a place similar to Costco, Sam’s Club or your local gym that snaps your photo for their records.

In the following image you can see how a tab has been added to the Contact form using the CRM customization capabilities.



A Silverlight 4 application is then hosted inside that tab that will provide the user experience for capturing the images. When the Start Camera button is clicked the user will be prompted to approve the access and the video feed will begin as you can see below.


The video feed will keep showing the live image updated from the web cam until stopped. The Capture button on the above application allows the user to capture one of the image frames from the capture source. The AsyncCaptureImage(..) method on the CaptureSource class allows you to request that a frame be captured and your callback invoked. The callback is then invoked and passed a WriteableBitmap representing the captured frame.


This image can then be saved back to the Dynamics CRM server and associated with the record being viewed.

In the above example we looked at how you could use the video capabilities to capture a static image. More advanced applications are also possible for things like collaboration by showing the real time audio and video feed of multiple users.

You have been reading about one of the many new and exciting features of Silverlight 4 that are covered in the complete overview chapter. Visit today to access the full chapter.

Posted on Wednesday, November 18, 2009 8:23 AM | Back to top

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