https://forum.unity3d.com/threads/upgraded-mono-net-in-editor-on-5-5-0b4.433541/
이게 사실이라면 미쳤네....
Here is a build matching our 5.5.0b4 beta release with the using the latest version of Mono (4.6+):
http://bit.ly/latestmono1
NOTE: This is an EDITOR ONLY build. The runtime players are not shipped with this release.
Please post any issues you have as a new thread on this forum and tag the posts with Mono Upgrade
Please backup your project before trying this build.
Important Notes
- No playback runtimes are included with this release. This means you can not build any player executables.
- Managed debugging via Visual Studio Tools for Unity or MonoDevelop is *not supported* in this release.
- The compiler targets the C# 6 language.
- The compiler *by default* will still target the .Net 2.0/3.5 framework profile we previously supported. However, you can change this to target .Net 4.6. (See below for instructions)
- The updated Mono garbage collector (SGen GC) is not enabled in this build. That will be enabled after the new Mono runtime and class libraries are viewed as stable.
FAQ
How will this affect me?
This upgrade should “just work”; except we don't expect it to be stable. 
What does Editor only actually mean?
There are no runtime players included with this installer. This means that if you open the build menu, you will not be able to Build or access the player settings menu from the Build Menu. See below to learn how to target .Net 4.6.
How do I target .Net 4.6?
Edit -> Project Settings -> Player
Under the Optimizations section, choose .Net 4.6 for the Api Compatibility Level:
*Look at it... Glorious.
What should I be testing/looking for?
We mostly want to know that this doesn't break existing code. Please trying running your projects in Play Mode in the Editor and let us know how it goes. If everything works, go ahead and try some new C#/.Net Features.
Are there any breaking changes?
Yes, there is one known breaking change. The new compiler has a change to how a closure captures the foreach variable. This was a breaking change the C# language team made. See previous posts about compiler upgrade or here for details.
Why don't we target .Net 4.6 / C# 6?
Did you read? This is it. We're almost there. Help us test!
Visual Studio Tools for Unity
The VSTU team has provided us with an unsupported and experimental build to support the changes in this preview. This is a custom build of VSTU 2.3 that supports Visual Studio 2015 only. Installing this build will overwrite any existing installation of Visual Studio 2015 Tools for Unity.
Get this special installation here: https://oc.unity3d.com/index.php/s/vWeoLpPGgovEkAE
if you want to reinstall the latest supported build of VSTU for Visual Studio 2015 just head over tohttps://visualstudiogallery.msdn.microsoft.com/8d26236e-4a64-4d64-8486-7df95156aba9
Last edited: Sep 28, 2016
