How do I disable C# 6 Support in Visual Studio 2015?
Background
We have a project that we're developing in VS 2015 with C#6 enabled that occasionally needs to be opened by developers using VS 2013 without C#6.
We have no intention to use C# 6 within this particular solution (as much as I'd like to).
Problem
Visual Studio and ReSharper suggest helpful C# 6 language constructs that render the solution inoperable in earlier versions of Visual Studio without C#6 support.
I've disabled the ReSharper C#6 support but I can't seem to disable / limit C# features across the whole solution.
Question
How do I limit C# to C#5 capabilities within a solution or within Visual Studio 2015?
Answer
You can set the language feature for each project separately by going to Properties => Build tab => Advanced button => Language Version and set your preferred version.
You should realize that it will still use the new "C# 6.0" .Net Compiler Platform (codenamed Roslyn). However, that compiler will imitate the behavior of older compilers and will limit you to features only available on that specific language version.
I don't think that there's a solution-wide setting available.