visual studio 2010 - How to reference .NET 4.0 assembly within .NET 3.5 projects

Question

I would like to do some Office Interop stuff using .NET 4.0, but developing the rest of my project using VS2008 and .NET3.5.

How can I now use the functionality from the .NET 4.0 assembly within my other solution. Loading CLR 4.0 assemblies into a 2.0 AppDomain won't work, will it?

Answer 1

In short: you can't.

.NET 4.0 is a totally new CLR (4.0) and as far as I know, cannot be intermixed with .NET 3.5 and/or used from VS 2008, sorry.

You could use .NET 2.0 assemblies from your .NET 4.0 code, if you also have a guarantee that the .NET 2.0 framework is on your target machine at the same time (side-by-side) with .NET 4.