Welcome to C# 7.1
https://blogs.msdn.microsoft.com/dotnet/2017/10/31/welcome-to-c-7-1/ [blogs.msdn.microsoft.com]
2017-11-03 16:15
In August of 2017 we shipped the first point release of C#. It’s called C# 7.1, and its main purpose is really for us to get practice with point releases, without having too many dependencies on accompanying technology to complicate matters. C# 7.1 is therefore a small release with just a few (but well-chosen) new language features; useful we think, but definitely in the minor range.