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As we’ve noted before, Visual Studio 2008 doesn’t have multi-targeting support for Silverlight development.  Generally speaking what this means is that if you install the Silverlight 3 tools, you have a Silverlight 3 development environment with VS2008.  True multi-targeting for Silverlight in the IDE will come in Visual Studio 2010 (you can see how that works in this post).

NOTE: Visual Studio 2010 beta 1 (current version available at the time of this writing) does not fully support Silverlight 3 *release version* (also referred to ‘RTM’ or ‘RTW’) development.  There are a few things missing in VS10 beta 1 for full support for SL3 RTW and .NET RIA Services development.  This support will come in later beta builds of VS10 – and no, I have no idea when Visual Studio will be planning on releasing additional beta builds.

But people still want to know how they can build SL2 apps using a single VS2008 machine, no virtual images and without VS2010.  There is a way to do this, but please allow me to set some major caveats.  We must first make sure that what I’m saying here is still that VS2008 does not support multi-targeting IDE development with Silverlight 2 and Silverlight 3.  What I’m also saying is that VS2008 IDE and MSBuild are two different experiences.  MSBuild could care less about an IDE and it just does what it is instructed to do…so let’s instruct it to build Silverlight 2 code, shall we?

Assumptions – please read

Let’s assume this scenario: you are working on SL3 apps so you need the SL3 tools.  Great – install them.  But you also need to either a) support an SL2 application and/or b) for some reason you want to start a new project in Silverlight classic…err, I mean…Silverlight 2.  Okay, let’s proceed with these assumptions and that you already have VS2008 and SL3 dev tools installed.

Step 1: Install the Silverlight 2 SDK

Go grab the Silverlight 2 SDK.  This is different than the Silverlight 2 Tools for Visual Studio.  Don’t install those…you’ll be made at me for no reason if you do.  Again, install the Silverlight 2 SDK.  Once you’ve done that, if you look at your %ProgramFiles%\Microsoft SDKs\Silverlight directory you will see both SDKs installed:

SDK directory with both Silverlight SDKs

Step 2: Create a new project or open your existing Silverlight 2 application

If you are creating a new application and are targeting Silverlight 2 and not taking advantage of all the great new features in Silverlight 3, then create a new Silverlight application.  Obviously (or hopefully so) you cannot choose the Navigation or RIA Services templates…you’ll have to choose the basic Silverlight 2 Application template.  If you are working on an existing SL2 application, open that project.  In this case, VS will convert the project up to an SL3 project.  This is fine for now.

At this point you have your application open in VS and it is basically a SL3 application project.  If you hit F5 at this point, it would build as an SL3 application.

Step 3: Make a copy of the .csproj or .vbproj file

Go to your project’s directory in explorer (fastest way to do this is right-click on the project in Solution Explorer and choose Open Folder in Windows Explorer which is second to the last option by default.  Once in Explorer, make a copy of the .**proj file (either .csproj for C# or .vbproj for Visual Basic).  Name it whatever you want, maybe something like <projectname>-SL2.csproj.

Open that file in notepad or other plain text editor.  You’ll see a line that looks like this (for a default project this is about line 84 – and note the CSharp.Targets will be different if you are using VB):

   1: <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Silverlight\v3.0\Microsoft.Silverlight.CSharp.targets" />

Notice the “v3.0” in the build path?  Alter that only in your copied **proj file to this: (again, noting the difference between CSharp and VB):

   1: <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Silverlight\v2.0\Microsoft.Silverlight.CSharp.targets" />

Basically change the “v3.0” to “v2.0” in that Import node.  This tells the build system to use the SL2 SDK that you installed in Step 1.

Step 4: Modify your build events in VS

At this point, if you still hit F5 you’d be running a SL3 application.  This is still because a) you aren’t opening the altered **proj file we just created in Step 3 and b) you have SL3 tools installed for VS.  What we need to do is instruct Visual Studio to perform an additional build command for your project.

Right-click on the project and select the project properties.  Then from here choose the Build Events tab.  If you really want only a v2 build of your app, then in your post-build event you can enter this (obviously changing to the file name you created in Step 3:

   1: $(MSBuildBinPath)\MSBuild "$(ProjectDir)SilverlightApplication1_2-SL2.csproj"

And when you F5 you’ll end up with a Silverlight 2 XAP.  Go ahead and look at the generated AppManifest.xaml file…it will show you RuntimeVersion=”2.0.31005.0” in the file.

What just happened?

Basically when you F5 in Visual Studio in projects, you are initiating build commands.  Sometimes you’ll see that it just uses csc.exe, but basically these are all build commands in the system.  What we’re doing in Step 4 is telling Visual Studio: When you’re done with that, go ahead and execute this additional build command for me, kthxbye.  Some may look at this and ask if 2 builds are happening.  The answer is YES.  Issuing a build command in VS does its normal process and then we are OVERWRITING THE OUTPUT with our second build.

NOTE: If someone has a better way to tell VS don’t do your normal build but do this instead please post in the comments…I’m not a VS build system pro.

You are definitely overwriting your SL3 compiled bits with the new ones.

Can I build both SL2 and SL3 from the same base?

Sure.  You’ll have to modify the OutputPath setting for your projects so they don’t overwrite each other.  I’m sure if you are asking this question you have a good reason for it as SL2 apps are compatible running under the SL3 runtime without needing to recompile.  I modified my VS IDE app on the Build tab (in the Properties dialog) to put the output in an SL3 folder.  I then modified the OutputPath setting in my file from Step 3 to a folder called SL2.  Now when I build in VS I get both binaries/XAPs created:

post build directories

So I can do what I want with the XAPs now.

So, what’s the catch?  Isn’t this multi-targeting?

Big catches…and NO, this isn’t multi-targeting for VS2008 (at least what we define it for Visual Studio).  Here’s the catches I’ve found:

Your IDE is still a Silverlight 3 IDE environment.  What I mean by this is that VS is doing nothing to prevent you from writing Silverlight 3 code.  Intellisense will be targeted at the SL3 SDK you have installed.  This means if you aren’t paying attention and don’t know what APIs aren’t available in SL2, you can get into trouble VERY fast.  In this event, if you do add code that is SL3 specific your SL2 SDK MSBuild will error out and report back in VS.  Here’s an example of where I added some element-to-element binding in my XAML and VS reports the error for the post-build event (as reported in the Errors output window):

   1: Error    2    The property 'ElementName' does not exist on the type 'Binding' in the XML namespace 'http://schemas.microsoft.com/winfx/2006/xaml/presentation'.    C:\Users\timheuer\Documents\Visual Studio 2008\Projects\SilverlightApplication66_3\SilverlightApplication1_2\MainPage.xaml    10    61    SilverlightApplication1_2
   2: Error    3    The command "C:\Windows\Microsoft.NET\Framework\v3.5\MSBuild "C:\Users\timheuer\Documents\Visual Studio 2008\Projects\SilverlightApplication66_3\SilverlightApplication1_2\SilverlightApplication1_2-SL2.csproj"" exited with code 1.    SilverlightApplication1_2

My SL3 build will still complete fine, remember the SL2 is a post-build event.

The other thing is copying files to an associated web project.  In my steps above, the XAP that would get copied to the ClientBin directory of the web app was the SL3 version.  Honestly I didn’t take the time to worry about that and I know that you could get more creative with your build command to change that…but I wanted to be clear about the output of my steps outlined here.

Assembly references will be another issue.  Remember, VS is doing nothing to prevent you from doing things SL3-specific.  So the assembly reference list you see will include SL3-specific binaries.  Also when you add references in VS, it alters the **proj file.  So each time this happens you’d have to manually edit your copied file to make sure the references are there and are the correct ones for the SL2 SDK.  This can get messy very fast.

What if I just want to continue doing Silverlight 2 development, but view SL3 sites?

Well, then I need to come over there and talk to you about the aweseomeness of Silverlight 3!  But if you must, let me let you know what is going on here.

Short answer: don’t install the SL3 tools.  But again, you’re crazy right?  Silverlight 3 is awesome!

Longer answer…

The Silverlight 2 Tools installer now installs the Silverlight 3 developer runtime, but still installs the SL2 SDK.  Confusing huh?  Bottom line is that in this configuration you can develop SL2 apps in the IDE (with SL2 Intellisense, assembly references, etc) but still be able to view SL3 sites out on the Internet.  How is this possible?  Because the SL2 tools are using the build commands and VS hooks for SL2 SDK (look at the project file and you’ll see it is like above in Step 3).

If you have SL2 tools already installed but don’t have SL3 yet…you cannot install the end-user SL3 runtime on top of a developer runtime (i.e., you cannot ‘upgrade’ a developer runtime to a non-developer runtime).  So you’ll want to install the SL3 developer runtime on top of your SL2 environment in this situation.


I do not by any means consider this guidance from the Silverlight team.  This is, in fact, a hack.  It’s unsupported, might not work for your situation and as Scott Hanselman says, it may hurt baby kittens.  This information is merely here to really prove a point that you can use MSBuild to build Silverlight 2 applications with the Silverlight 2 SDK.  That’s really the end output here.  The rest is hackery to get VS to do things with that build.  I firmly recommend you develop using Silverlight 3 anyway!

Use at your own risk.  If there are other MSBuild professionals out there that have better methods than post-build events, please comment – again, I’m not a pro in that area, so this was my first pass at testing this out based on questions I got from the community.

Hope this helps and don’t blame me for any injured baby animals.

This work is licensed under a Creative Commons Attribution By license.

7/17/2009 3:15 PM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
I also noticed that the SL2 SDK installed SL3 on my new machine without asking me. That is NOT as awesome as you think, but horrendously bad. If I want to build for SL2, and also want to make sure that it runs correctly against SL2 and that it is certified to work on those machines that still has SL2. I know that SL2 apps are supposed to run just fine for SL3, but that's all theory, and testing should always happen with both runtimes.

What I'm really asking is how I can avoid getting the SL3 runtime when I need the SDK installed? It is not intuitive that I get SL3 when I install SL2 SDK, and I could imagine a lot of people who never right-click their app and browse to the SL settings and realize that they are actually not testing on the SL2 runtime.
7/17/2009 3:23 PM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
Morten - in this case (where you must test against SL2 runtime running) -- you should isolate machines (or have a test machine with only the runtime running). As I mentioned -- this is a hack for sure. If you want to avoid getting the SL3 runtime, then you need to download the SL2 dev runtime first and follow the offline instructions to install the SL2 tools and Sl2 dev runtime. Then make sure your preferences are set not to auto update the runtime.

Note that even though you have the SL3 dev runtime installed by the tools it is still compiling to SL2 and thus running in SL2 mode.
7/17/2009 8:26 PM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
Sure. All I was saying is that I think it was a bad practice to install SL3 when you think you are installing SL2. You are already making a deliberate choice to install SL2, considering you guys almost have hidden the SL2 download :-)

Even though SL3 can run in SL2 mode, as I understand it from the change list there are still some differences between "true SL2" and "SL3 minus 1" :-).
7/17/2009 9:19 PM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
Hi Tim,

I degraded from SL3 to SL2 following the steps posted here blogs.msdn.com/.../...-to-silverlight-2-tools.aspx
Everything works great until I try to open my page.xaml in Blend 2. It says that I have an invalid SL2 project. Any suggestions?
7/17/2009 9:21 PM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
Morten - I can appreciate where you are coming from. Just to clarify as well -- the changes you refer to in SL3-1 ;-) are called quirks mode and actually the mode enables SL2 *compiled* apps to run using SL2 behavior for those areas (of which are documented). If the code is recompiled in SL3, then there are the differences you'll have to consider.

Todd - I'm not sure Amy updated her scripts for SL3 RTW -- what her script basically does is uninstall/re-install things each time you switch.
7/20/2009 1:06 AM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
Great article! It provides valuable insight into the inner workings of VS and Silverlight. A lot of people can learn something here.
7/20/2009 10:59 AM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
The problem with this approach is that when you test your SL2 app on your SL3 machine, it will be running in the SL3 runtime. If you are building or supporting an SL2 app, it should be tested in the SL2 runtime so that you can reproduce any issues there that have been fixed in SL3. I'll continue using a separate VM for now, though fortunately we'll be shipping SL3 versions of my SL2 apps soon.

It's really disappointing that multi-targeting isn't supported out of the box. If I open up the Flash IDE, I can publish back to Flash Player 1 if I want.
7/20/2009 12:19 PM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
Josh -- Thanks for the feedback. Is the "running under SL3" a trust issue? What's the concern? That SL3 doesn't *really* render SL2 content the same?

As to the Flash IDE, etc. -- the underlying architecture of Flash is fundamentally different than .NET. We also are providing tools on an already shipping platform (VS2008) where the real challenge is. We'd have to rev VS in total (multi-targeting is at the core) versus just the add-on tools. I agree with you that I wish it was there too though :-(
7/21/2009 9:17 AM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
the only thing keeping me from using Silverlight 3 is this ObjectAnimationUsingKeyFrames regression:

do you know of any workarounds?
7/22/2009 11:36 AM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
Thank you for the blog! Silverlight and RIA Services are so exciting!!

So far, the one thing I can't find any information about is CRUD to the server file system through RIA Services.

I have a project from a client where the ability to administer a subfolder on the server-side is central (CRUD directories and files within a subfolder in the web app). I'd love to be able to do this project with SL3 and RIA services!

Is this possible at this time? If so, is there any chance someone could share some working examples on how to do this with SL3 and RIA Services?

Thank you so much for your time and sharing your knowledge :-)

7/22/2009 11:49 AM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
Ben -- take a look at the walkthrough here silverlight.net/learn/learnvideo.aspx?video=245417. As I indicate in the walkthrough -- you own the CRUD functions on the server...so they can do what ever you want.
3/1/2010 3:08 PM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008

Your article was very helpfull and just what I was looking. You see ESRI is using Silverlight 2.0 for all their ArcGIS maps and they recently upgraded their online silverlight site to 3.0 so since I was doing all my development in sivlerlight 2.0 so I could no longer see the ESRI silverlight samples. If I upgrade my local development environment then I can no longer support the WPF project I have in silverlight 2.0. So you see these things get even more messier when there is a third party control you are using. In this example, ESRI Interactive SDK which is written in Silverlight 2.0 also stopped working for me because I upgraded my environment to SL3. This is really a big issue if you are looking at multiple vendors like Infragistics, Telerik etc and if they will be releasing their controls and code for a particular runtime then it will be tough to keep track of how to compile everything from one machine. I am using virtual machines to get by but still it is a hassle. Anyway, thanks for your article, it is definitely a solution.
4/15/2011 4:30 AM | # re: Building Silverlight 2 and 3 applications with Visual Studio 2008
gud one!!

Please add 1 and 3 and type the answer here:


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