VS 2008 Multi-Targeting Support

Thats valuable, Scott Guthrie is describing how the multi-targeting works into new named VS 2008. The idea is to have the new IDE working with 2.0 framework. Unfortunately 1.1 isnt supported. Here is his post:

Earlier this month at TechEd we announced the official name of Visual Studio “Orcas” – which will be called Visual Studio 2008. We also said that the official name for the .NET Framework “Orcas” release will be called .NET Framework 3.5 (it includes the new LINQ support, integrated ASP.NET AJAX support, new ASP.NET data controls, and more).

VS 2008 and .NET 3.5 Beta 2 will ship later this summer, and the Beta 2 release will support a go-live license for those who want to put applications into production using the new features immediately.
What is Multi-Targeting?

With the past few releases of Visual Studio, each Visual Studio release only supported a specific version of the .NET Framework. For example, VS 2002 only worked with .NET 1.0, VS 2003 only worked with .NET 1.1, and VS 2005 only worked with .NET 2.0.

One of the big changes we are making starting with the VS 2008 release is to support what we call “Multi-Targeting” – which means that Visual Studio will now support targeting multiple versions of the .NET Framework, and developers will be able to start taking advantage of the new features Visual Studio provides without having to always upgrade their existing projects and deployed applications to use a new version of the .NET Framework library.

Now when you open an existing project or create a new one with VS 2008, you can pick which version of the .NET Framework to work with – and the IDE will update its compilers and feature-set to match this. Among other things, this means that features, controls, projects, item-templates, and assembly references that don’t work with that version of the framework will be hidden, and when you build your application you’ll be able to take the compiled output and copy it onto a machine that only has an older version of the .NET Framework installed, and you’ll know that the application will work.

So why use VS 2008 if you aren’t using the new .NET 3.5 features?

You might be wondering: “so what value do I get when using VS 2008 to work on a ASP.NET 2.0 project versus just using my VS 2005 today?” Well, the good news is that you get a ton of tool-specific value with VS 2008 that you’ll be able to take advantage of immediately with your existing projects without having to upgrade your framework/ASP.NET version. A few big tool features in the web development space I think you’ll really like include:

1. JavaScript intellisense
2. Much richer JavaScript debugging
3. Nested ASP.NET master page support at design-time
4. Rich CSS editing and layout support within the WYSIWYG designer
5. Split-view designer support for having both source and design views open on a page at the same time
6. A much faster ASP.NET page designer – with dramatic perf improvements in view-switches between source/design mode
7. Automated .SQL script generation and hosting deployment support for databases on remote servers

You’ll be able to use all of the above features with any version of the .NET Framework – without having to upgrade your project to necessarily target newer framework versions. I’ll be blogging about these features (as well as the great new framework features) over the next few weeks.

What about .NET 1.0 and 1.1?

Unfortunately the VS 2008 multi-targeting support only works with .NET 2.0, .NET 3.0 and .NET 3.5 – and not against older versions of the framework. The reason for this is that there were significant CLR engine changes between .NET 1.x and 2.x that make debugging very difficult to support. In the end the costing of the work to support that was so large and impacted so many parts of Visual Studio that we weren’t able to add 1.1 support in this release.

VS 2008 does run side-by-side, though, with VS 2005, VS 2003, and VS 2002. So it is definitely possible to continue targeting .NET 1.1 projects using VS 2003 on the same machine as VS 2008.

What is compatibility like moving from VS 2005 to VS 2008 and .NET Framework 2.0 to 3.5?

We are trying to make sure that .NET Framework 3.5 is a super compatible upgrade from .NET 2.0, and not require you to change any code in order to target the new framework version. We’ve deliberately made only non-breaking modifications to existing .NET assemblies in the .NET 3.5 release, and where possible added new features in separate assemblies to minimize the chance of breaking changes.

We are also not making project model or build changes with VS 2008. I, like you, hope to never to go through that again! Both the “web site” and “web application project” models will be fully supported going forward.
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