I created a project in Visual Studio 2017 RC to check whether I can use new C# 7.0 language features in a .NET Framework 4.5 project. It seems to me that after referencing <
Running a C# 7 compiled application on .NET 4.5 should be fine at this moment, but note that running ASP.NET applications that use ASP.NET Dynamic Compilation won't work on .NET 4.5 because the C# 7.0 compiler requires .NET 4.6 to run.
Source: https://github.com/dotnet/roslyn/issues/17908:
The C# 7.0 compiler (2.0 and higher) requires .NET 4.6 to run
The information on https://www.nuget.org/packages/Microsoft.Net.Compilers/2.0.1 (about supporting .NET 4.5) seems to be outdated.