You might have noticed that the Silverlight 5 (Release Candidate) is out. One of the new features included in the RC
is the ability to call P/Invoke. In this short demo, we will write a Silverlight 5 application that uses the feature.
Go ahead and open Visual Studio 2010 SP1 and select File->New Project, then Silverlight Application.
By default, we have a new option called “Silverlight 5” selected as the Silverlight version. Let’s go ahead and leave it at that. You also have the ability to select
Silverlight 3 or 4 from this drop-down.
Let’s go ahead and right click on our project and select Properties.
Put a check in “Enable running application out of the browser”.
Now go ahead and put a check in “Require elevated trust when running outside the browser”.
Switch back over to MainPage.xaml and add in the following code:
<Grid x:Name="LayoutRoot" Background="White">
<Button Height="23" HorizontalAlignment="Left" Margin="169,132,0,0"
VerticalAlignment="Top" Width="75" x:Name="btnclick"
Content="click" Click="click_Click" />
This will simply put a no thrills button on the page that the user can press to call the P/Invoke code we will add shortly.
Let’s go ahead and add a new class to the project.
Let’s call it PlatformInvokeTest.cs and add the following code (Note: If you are having a problem getting it to work, then use my solution at the bottom of the post):
public class PlatformInvokeTest
public static extern bool Beep(int frequency, int duration);
public static void PlaySound()
Random random = new Random();
for (int i = 0; i < 50; i++)
Let’s switch back over to MainPage.xaml.cs and add the following code:
public partial class MainPage : UserControl
private void click_Click(object sender, RoutedEventArgs e)
Now when the user fires up this project, the application will go out of browser and the computer will beep multiple times in a different frequency each time.
You can also get this same functionality in-browser by going back to the Properties page and selecting “Require elevated trust when running in-browser”.
The only thing to note is that the .aspx page is no longer set to the default in your web project so you will need to do a “View in Browser” on your
.aspx page in order to test.
As you can see, it is very easy to use P/Invoke in a Silverlight 5 application. This sample was pretty simple but imagine the possibilities such as detecting when a USB
key is inserted into a PC and copying files onto it through a Silverlight 5 application. Pretty cool stuff!
If you want the source code to this application and other Silverlight 5 demos, then be sure to check out
Michael’s “Mega Collection
of #Silverlight 5" Demos.
Other Silverlight 5 resources by me are listed below:
Michael Crump is a Silverlight MVP and MCPD that has been involved with computers in one way or another for as long as he can remember, but started professionally in 2002. After spending years working as a systems administrator/tech support analyst, Michael branched out and started developing internal utilities that automated repetitive tasks and freed up full-time employees. From there, he was offered a job working at McKesson corporation and has been working with some form of .NET and VB/C# since 2003.
He has worked at Fortune 500 companies where he gained experience in embedded systems design and software development to systems administration and database programming, and everything in between.
His primary focus right now is developing healthcare software solutions using Microsoft .NET technologies. He prefers building infrastructure components, reusable shared libraries and helping companies define, develop and automate process standards and guidelines.
You can read his blog at: MichaelCrump.net
or follow him on Twitter at @mbcrump