使用较旧的.NET版本和较新的C＃版本的副作用

Question

I wrote some code in .NET Project on a windows 10 machine with visual studio 2017. The target framework ist 4.5.2. and the used C# version is default (running the csc tool under "C:\\Windows\\Microsoft.NET\\Framework\\v4.0.30319" shows C# 5.

I have used a feature from C# 6. The Monadic null checking ( https://damieng.com/blog/2013/12/09/probable-c-6-0-features-illustrated ). and the compiler doesn't complain about it.

Is that a normal bhaviour or am I missing something? Shouldn't the compiler complain about it?

Answer 1

What you're missing is that the C# compiler being used isn't the csc.exe you found. Visual Studio comes with its own C# compiler which supports C# 6 (and later, depending on the exact version of VS you've got installed).

Answer 2

C# language version is decided by Visual Studio, not by .Net Framework.

As long as your Visual Studio version supports the C# version you will not face any error.

Configuring Language version in Visual Studio: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/configure-language-version