ASP.NET MVC C# Language Level - Not working


Visual Studio 2017 v15.2
R# 2017.1.2

I have an ASP.NET MVC project which builds and runs correctly. R# is consistently telling me that every single view is an error, because it is using a C# 6 language feature.

  • I have tried clearing the caches and restarting VS.
  • I have tried clearing the caches, closing VS, and deleting the "_ReSharper.Caches" folder.
  • I have tried setting the language version in the Properties -> Build -> Advanced dialog.
  • I have tried explicitly setting the R# "C# Language Level".

The errors persist.

I do not have time to re-create this project from scratch!

Please tell me I have an option to fix this BUG without disabling R#.

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Official comment

Hello Richard

Please try setting the compiler version in web.config to a numeric value (/langversion:6) -


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Also, attempting to report this as a bug from within Visual Studio returns the error "Connection refused". Where's the button to report a bug with the bug reporting feature?!

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Updating to R# 2017.1.3 makes no difference.

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Downgrading Microsoft.Net.Compilers from 2.2.0 to 1.3.2 seems to have fixed the problem. But why?

I can understand R# not knowing about a newer version of the compiler; but why would explicitly setting the C# language level to 6.0 not actually tell R# to allow C# 6.0 language constructs?

And when will R# be updated to support the newer versions of this package?

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Aaargh! That's got it, thanks.

It was already set to 6, but the updated NuGet package reset it to "default" for some reason.


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