Unity 4.3 Mono 4.0.1 and the .NET 3.5 to 4.0 Library issue

Hello, I was wondering, while Unity 4.3 uses Monodevelop 4.0.1 (and the subsequent .NET 4 equivalent) why is Unity stuck with the .Net 3.0/3.5 equivalent? I ask because I’m trying to use a library that targets 4.0 but it doesn’t work because it says the project is built for 3.5.

If that question isn’t clear, is there a way of using 4.0 and then layering with 3.5 calls?

An update: So I have used .NET 4 as the target platform and Unity still is having issues with it.

You cannot call a library from .net 4 unfortunately. I recently came up against this issue when i wanted to use a large program in a port to Unity. The solution was to run the original program as a service and then have my Unity program call that service to get its results in a serialized form.

Okay, I’ve been working on it but there have been errors trying to make the project 4.0. Anyone have any suggestions on this scenario?