It would be nice to be able to target different versions of C#, even the lower ones. It would help in prototyping code that will be added to legacy applications that don't support newer features. Also, being able to use newer features would be a plus as Roslyn provides support.
>C# 7.1 is now supported through newer Roslyn APIs, which means you can now use default literal expressions, and inferred tuple element names. The VB.NET compiler has been refreshed, too.
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http://www.linqpad.net/Download.aspx#beta
I'm not sure about the value of supporting older C# versions, unless it can also let you target older Framework versions (which is more complicated).
Thanks for fast update!
Pattern matching with generic also available in new version of C#.