Can a Visual Studio 2010 Package be installed in Visual Studio 2008?

Question

I wanted to have a Visual Studio package that is loadable in VS2008. To do so I've followed these steps:

1. Created a new package project in VS2008 and made sure it loads fine
2. Ported the project to VS2010 format, compiled there and made sure it works.
3. Then I changed the target framework to .NET 4 and when I compiled, I got the following message: regpkg : error : Could not load file or assembly 'file:///C:\\SVN\\Debugger\\src\\Visualizer2008\\bin\\x86\\Debug\\Visualizer2008.dll' or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded. regpkg : error : Could not load file or assembly 'file:///C:\\SVN\\Debugger\\src\\Visualizer2008\\bin\\x86\\Debug\\Visualizer2008.dll' or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded.

Questions

1. Is it possible, in the first place, to have a .NET 4 package loaded into VS2008?
2. If it is, then what can I do to register it successfully?

Thanks!

Answer 1

Packages loaded into Visual Studio 2008 will always use the 2.0 CLR. Things that target the 4.0 CLR cannot be loaded into VS 2008 because of the incompatibility. You need to target .NET 3.5 or below for a package to load in 2008.