We only have Visual Studio 2005. We're developing an application for Windows Mobile 6 and would like to use the .NET Compact Framework 3.5. However VS 2005 defaults to the 2.0 framework (for Windows Mobile 5).
It all works fine, but I would still like to use the 3.5 framework. Is this possible in some way?
Yes, it is possible to develop applications with Visual Studio 2005 for Windows Mobile 6 (Standard, Classic, and Professional). You will need to install the SDK for the platform.
Ref.
If you can move to Visual Studio 2008, I would do so.
You should be able to reference any .Net 3.5 assembly in VS 2005, by manually referencing assemblies in the %ProgramFiles%\Reference Assemblies\Microsoft\Framework\v3.5 folder.
However, you will obviously not get the .NET 3.5 support you get with VS 2008. That means no extension methods for example, which is the prerequisite for any LINQ stuff.
If I were you, I will try to use SharpDevelop (to build everything on .NET CF 3.5) along with Visual Studio 2005 (debugging and deployment) as a workaround.
However, using Visual Studio 2008 is still the best choice.