Download Sample Code: SilverlightPlayground.SL4BetaTestConsole.zip (89K)

During the Keynote of the PDC 2009 a new beta of Silverlight has been announced and made available. I think very few people did expect the early release of the version 4.0, and if you think in terms of number of new features compared with the time passed since the RTW of Silverlight 3.0 - only four months - you understand the big work made by one of the most prolific teams of Microsoft.

In the latest month I could play with the beta bits, and I've compiled a collection of the most important features coming in this release, to understand how them works and to release some working code to let people easily learn them. This collection is linked at the end of this post in the form of a self-explaining navigation application. The application contains eleven samples that show the features I list below:

Full Trust in Out of Browser: While detaching an application to out of browser now it is possible to give full trust to the installed application. This enable huge improvements: no need of cross domain policies, access to file system, no user-initiated dialogs. You can also use COM interoperability.

WebCam: Silverlight 4.0 introduce some new API to handle video and audio capture. This sample shows how to use the CaptureSource class to detect video devices and to capture live stream and snapshots from it. The same pattern can be used to capture audio sources

WebBrowser: This new control has been added to the Silverlight bits to enable the use of html hosting into Silverlight applications. The WebBrowser control is available only when the application is running out of browser so before running the sample you need to install the application

RichTextArea: Another new control let the user enter formatted code. The RichTextArea behave like a TextBox but it can host fonts, weights, styles, and entering graphic elements and links like you can do with a text editor. The sample show also how to read the content of the RichTextArea you can populate with XAML markup.

HTML Brush: Like using a media element to publish a video on a brush with the HtmlBrush it is possible to use the output of a WebBrowser control to render the brush. The use of this feature has some limits but the code works fine.

PrintDocument: In the development of Line of Business applications, sending documents to the printer is an useful feature. Silverlight 4.0 introduce a new PrintDocument that enable sending elements of the Visual Tree to the printer.

Righ Mouse Button: In the previous releases the context menu of Silverlight prevent the use of the Right mouse button. In this release you can intercept this button and attach the logic you need. In the sample you can use left and right buttons to change the size of the circle. If you click outside the circle the normal context menu will be displayed.

DataBinding to DependencyObject: In the current version the DataBinding between elements is available only when the target inherits from FrameworkElement. This limit prevent, as an example, to bind multiple a RotateTransform to a single Slider. In Silverlight 4.0 this limit has been overcome and now it is possible to bind DependencyObjects. This is a great step in the compatibility with WPF.

Improvements to Binding: The binding markup extension has been enriched with a new set of properties which simplify the development. This include StringFormat, FallbackValue and TargetNullValue.

Commands: The controls inheriting from ButtonBase has acquired two new properties, Command and CommandParameter. It is a tiny step in the direction of MVVM programming.

Drag & Drop: With this release it is possible to detect dragging of elements on the application surface. The sample read the filename, la last access date and the size of the stream.

Notification Window: Desktop application can show a popup in the tray bar of Windows. This now is available also in Silverlight out of browser applications.

These are a huge set of features for the short period of time where they were developed. I hope many of you will find useful the code I've linked to this post. If you need help to understand the samples feel free to contact me through the contact form.

Download: SilverlightPlayground.SL4BetaTestConsole.zip (89K)

Some weeks ago I've worked on an exercise originally started to try writing a complete application with full Model-View-ViewModel pattern. I've created the application with Visual Studio 2008, Prism to integrate missing features and Ria Services July CTP to get access to a SQL Server 2008 Database.

The application is a little time tracker, and I've decided to attach it to this post because it was very useful to me to understand problems and missing things about the MVVM pattern.

In the next days I will write some words about these problems I found, but for now I only want to undisclose the application to let something download it and give me some comments about it.

If you decide to try the application remember to attach the database mdf in the zip file, to set the connection strings in the web.config and the credentials for reporting services if you want to setup it and finally enter "tracker" as username and p@ssw0rd as password.

I'm currently learning this pattern and I do not want to consider my implementation complete, perfect and without any error. So please let me know what do you think and how can I improve it. Thanks in advance.

Download: Elite.TimeTracker.zip (~820 Kb)

Using a Ria Services Class library to collect DomainServices and DomainContexts in a solution is a good practice because everyone know the value of having classes separated in projects instead of having them in the web project.

If you try to create this kind of project and then you add an Authentication Domain Service with the July 2009 CTP of Ria Services you will find two major drawbacks. First of all you will notice the generated code does not contains a RiaContext class. RiaContext is the class responsible to handle the User and roles and configure the type of Authentication to use in the application.

To workaround to this problem you may simply write by hand this class and put it in the client side part of the Ria Services library project. The code can be copied by an AuthenticationDomainContext generated in the web project but it is very simple and I show you the code here:

   1: public sealed partial class RiaContext : System.Windows.Ria.RiaContextBase

   2: {

   3:     #region Extensibility Method Definitions

   4:  

   5:     partial void OnCreated();

   6:  

   7:     #endregion

   8:  

   9:     public RiaContext()

  10:     {

  11:         this.OnCreated();

  12:     }

  13:  

  14:     public new static RiaContext Current

  15:     {

  16:         get

  17:         {

  18:             return ((RiaContext)(System.Windows.Ria.RiaContextBase.Current));

  19:         }

  20:     }

  21:  

  22:     public new User User

  23:     {

  24:         get

  25:         {

  26:             return ((User)(base.User));

  27:         }

  28:     }

  29: }

With this class you can configure the Authentication Domain Context as you did with the generated class. So you have to add it to the App.config, in the ApplicationLifetimeObjects tag and then add a kind of authentication like the WindowsAuthentication and FormsAuthentication.

The second drawback is that if you run the project this way and then you call the Login() method (or any other method) of the RiaContext you will get an error:

The DomainContextType is null or invalid and there are no contexts generated from AuthenticationBase<T>

This probably come from the fact that the RiaContext is not correctly initializated so when the class search for a valid domaincontext to handle the Login call it fails because it does not find it. The tip to correct this behavior is to specify the DomainContext property in the Authentication you have choosed. Here is how to change the App.xaml file:

   1: <Application.ApplicationLifetimeObjects>

   2:     <slpgria:RiaContext>

   3:         <slpgria:RiaContext.Authentication>

   4:             <appsvc:FormsAuthentication>

   5:                 <appsvc:FormsAuthentication.DomainContext>

   6:                     <slpgdc:MyAuthenticationDomainContext />

   7:                 </appsvc:FormsAuthentication.DomainContext>

   8:             </appsvc:FormsAuthentication>

   9:         </slpgria:RiaContext.Authentication>

  10:     </slpgria:RiaContext>

  11: </Application.ApplicationLifetimeObjects>

As you can see you have simply to give an instance of the generated Authentication Domain context class to the FormsAuthentication (or Windows Authentication as well). The RiaContext need to have this instance to make the calls to the BL methods in the Domain Service.

I really do not know if this behavior will be corrected in the next releases of RiaServices. The solution is pretty simple but take me some hours to understand what are going wrong. So I hope this may help you to spare some time making your experiments with the current release.