Target the minimum necessary .Net framework

[rubberduck203]

Currently we're targeting the 4.5 framework, which is not supported by Windows XP. We can add support by targeting the 4.0 or 3.5 framework. We need to determine the minimum version necessary and target that instead. Obviously, 3.5 gives us maximum compatibility, but I'm not sure if/what features we're using that wouldn't be available.

List of Operating Systems Supported by 4.0 and 3.5.

[rubberduck203]

After further investigation, we might not want to target anything older than 4.5. We're using the async features that were introduced in 4.5. Sticking with 4.5 means the minimum OS for Rubberduck would be Vista. Considering XP has reached the end of it's lifecycle, I'm not sure we should uproot the code base to support it. On the other hand, there are many users out there still using XP, as evidenced by the user who brought this to our attention. Thoughts @retailcoder?

• https://twitter.com/danrfraser/status/572323348866326528/photo/1
• http://en.wikipedia.org/wiki/.NET_Framework_version_history

[retailcoder]

I don't think disabling the TPL & async code for a < 4.5 target would make a good UX. And not leveraging async/await and the Task Parallel Library means we need to implement multithreaded code ourselves.

Windows XP is out, officially not supported since almost a year now - we know our code can run on a Vista+Office97 setup, I don't think it's worth the effort to go out of our way to retarget for 4.0.

Hence, our minimum requirement is .net 4.5's requirements.

[rubberduck203]

Agreed, but I'm going to leave this issue open until we've documented minimum system requirements and adjusted the installer to enforce them.

[rubberduck203]

Added info to Wiki & ReadMe. I still need to address the installer.