Use .NET Standard 2.0 CommandLineParser, Update to net461 for NS2.0 support

[glennawatson]

• Added support for CommandLineParser 2.3.1 Net Standard 2.0 library -- this is for future work on support Xamarin releases
• Now use NET461 for the libraries, this is required for .Net Standard 2.0 support.
• Now use $(TargetFramework.StartsWith('net4')) in our csproj files, this allows upgrades to .NET 4 based libraries without the pain currently required.

[adamsitnik]

Hi @glennawatson

Thanks for the PR!

I am fine with moving from CommandLineParser to CommandLineParser.NS20 but I don't like the net46 -> net461 update.

Could you please provide a link to the issue that we try to solve? I want to get more insight into it.

I also want to switch from CommandLineParser to https://github.com/dotnet/command-line-api, but it's not available on NuGet.org yet (dotnet/command-line-api#356)

[glennawatson]

@adamsitnik you can't compile .net standard 2.0 libraries in your application with net46.

See https://blogs.msdn.microsoft.com/dotnet/2017/08/14/announcing-net-standard-2-0/
Broad platform support. .NET Standard 2.0 is supported on the following platforms:
.NET Framework 4.6.1
.NET Core 2.0
Mono 5.4
Xamarin.iOS 10.14
Xamarin.Mac 3.8
Xamarin.Android 7.5
Upcoming version of UWP (expected to ship later this year)

So if you want to use either th command line parser ns2 or th command line API your going to hit the same wall you need to upgrade to net461 otherwise you'll get compile errors.

[glennawatson]

commandlineparser/commandline#292 is the issue I am hitting. It's solved with commandlineparser/commandline#307 but again you can't get that fix without going to net461 due to it being the first version to support net standard 2.0. Net46 is not supported in that scenario

[ViktorHofer]

Just as a note, CommandLineParser.NS20 was published by me some months ago to overcome the time till my PR is accepted. Unfortunately that still hasn't happened.

[adamsitnik]

@AndreyAkinshin are you ok with the update from .NET 4.6 to 4.6.1?

I think that we will have to do it anyway since Roslyn's next version is going to support .NET Standard 2.0 only: https://www.nuget.org/packages/Microsoft.CodeAnalysis.CSharp/2.11.0-beta1-final

(the lowest .NET supporting .NET Standard 2.0 is .NET 4.6.1)

[AndreyAkinshin]

In general, I don't like the .NET 4.6->4.6.1 update. However, I understand that it will simplify future development a lot. Let's do it.

In the future, we can introduce the BenchmarkDotNet.Annotations NuGet package (we already discussed this idea before) with low runtime requirements (e.g., .NETStandard 1.0; .NET Framework 3.5). We don't actually need .NETStandard 2.0 in the benchmark source code. Such benchmarks can be executed with the help of our global tool. =) I guess, it will require a major refactoring and some hacks here and there, but it looks like a good approach.

[adamsitnik]

@AndreyAkinshin @glennawatson thanks!