Need to determine which .NET Core SDK has which C# version enabled

[BillWagner]

We explain which C# version ships with which release of Visual Studio. @damtur raised this issue after a talk that he could not find that mapping for the versions that ship with .NET Core SDK versions. For example, which .NET SDK has C# 7.1? or 7.2? This make affect the dotnet CLI, as the compiler ships as a dotnet tool.

We need to make this more prominent if it is published. If not, we need to publish it more prominently.

/cc @richlander @jcouv @KathleenDollard

[jcouv]

Tagging @livarcocc for this

[BillWagner]

As a work around, you can add an error pragma to the source to print the version:

#error version

This cause the compiler to print its version (the compiler software version, not the project LangVersion) to the console. It also causes the build to fail.

[KathleenDollard]

I agree we need this.

Do we have a place in docs to put this?

[dasMulli]

cross-linking https://github.com/dotnet/cli/issues/8042 which raised some other questions in the process:

• How do I know what things I have in my .NET Core SDK (NuGet, MSBuild etc., not relevant here)
• How do I know which Roslyn version number corresponds to which C# version <-- hard part
  (https://github.com/dotnet/cli/issues/8042#issuecomment-356638924)

Same probably goes for F# since it now ships in-box.

[svick]

@dasMulli

How do I know which Roslyn version number corresponds to which C# version

This is documented in the Roslyn repo wiki article NuGet packages. Though including that information somewhere in docs.MS is probably a good idea.

[BillWagner]

@KathleenDollard said:

Do we have a place in docs to put this?

I'd suggest either the .NET Core "What's new" page, or coordinating with the ongoing versioning work.

[richlander]

I think we need two things:

• An entry in "What's new".
• a decorder ring table that explains what's in each release. This can go in docs or in a repo. It is probably best put in dotnet/core in release notes. Yes?

[svick]

Putting together information from NuGet packages on Roslyn wiki (which maps Roslyn versions, C# versions and VS versions), Releases on the cli repo (which maps .Net Core SDK versions and VS versions) and from my own attempts of running various versions of the .Net Core SDK, as far as I can tell, corresponding versions are:

Roslyn	C#	VS	.Net Core SDK
1.x	6.0	2015
2.0	7.0	15.0	1.0.4
2.1	7.0	15.1
2.2	7.0	15.2
2.3	7.1	15.3	1.1.4
2.4	7.1	15.4	2.0.2
2.6	7.2	15.5	2.1.2
2.7	7.2	15.6	2.1.100
2.8	7.3	15.7	2.1.200
2.9	7.3	15.8

[dasMulli]

In theory, it also bundles an F# compiler (and a version of NuGet but that's hardly relevant)

[BillWagner]

PR #6081 will fix this.

[BillWagner]

This was fixed in #6081

[colonelchlorine]

@BillWagner Not sure if #6081 solved the problem of this ticket. Having trouble finding the mapping of .NET Core <-> language version (C# in particular). svick's post above is the only thing I can find. Might be missing something?

Checked DotNet Core Versions and don't see the language versions that line up.

[BillWagner]

@colonelchlorine This paragraph has the information you need. It's the final paragraph in .NET Core Version History

We didn't add it to docs, but rather put it on the .NET Core downloads page. That way, it's always up to date.

Detailed information about the versions of individual components, including framework and language compiler versions, can be found on the .NET Core downloads page. For detailed information about previous versions, select the requested version from the .NET Core download archives page. Detailed support information can be found in the article describing the official .NET Support Policy.

[colonelchlorine]

Aha - bit tricky to find. Needed to go to the "Find more in .NET Core 2.1 downloads" or "download archives" from the Downloads page. The archive pages are full of useful info. Thanks @BillWagner