VS2015/VS2013 build broken when NuGet package is installed using VS2017.3

[oatkins]

This is related to #454, but not exactly the same.

We have a large .NET 4.6.2 Windows desktop application with many developers. Some are using VS2017, but many are still on VS2015 or 2013. When a developer working in VS2017 adds a reference to the latest version of System.Collections.Immutable, the project can no longer be built by older versions of Visual Studio. We see many errors like:

The type 'System.Collections.IStructuralEquatable' is defined in an assembly that is not referenced. You must add a reference to assembly 'netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'.

Installing NETStandard.Library.NETFramework does resolve the problem, but since the package is marked as a preview, it causes other build warnings when we try to generate NuGet packages from our projects.

This leaves us with three options, none of which is very appealing:

• Always add NuGet packages using VS2015. (We would prefer that developers do not need multiple versions of VS to be installed.)

• Have all developers install VS2017, even if they continue to develop in VS2013. (They can't: they don't have licenses.)

• Install the NETStandard.Library.NETFramework preview package in all our projects and try to find a way to suppress the warnings.

Am I missing any better alternative?

[oatkins]

The following is a minimal repro of a solution that builds fine in VS2017 but not in VS2013.

TestNetStandardNugetPackage.zip

[dasMulli]

For Visual Studio 2015 there is a NuGet 3.6.0 VSIX at https://www.nuget.org/downloads that tells me to download the VS 2015 support from https://download.microsoft.com/download/0/F/D/0FD852A4-7EA1-4E2A-983A-0484AC19B92C/dotnet-standard-support-vs2015-2.0.0-win-x86.msi (though via an aka.ms link that I now no longer have in my clipboard)

However, giving this a try on that solution yields compile errors for conflicting references like this:

CSC : error CS1703: Multiple assemblies with equivalent identity have been imported: 'C:\Program Files (x86)\MSBuild\Microsoft\Microsoft.NET.Build.
Extensions\net461\ref\System.Xml.XmlSerializer.dll' and 'C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6.1\Facades
\System.Xml.XmlSerializer.dll'. Remove one of the duplicate references. [C:\Users\martin.ullrich\Downloads\TestNetStandardNugetPackage\TestNetStandar
dNugetPackage\TestNetStandardNugetPackage.csproj]

Same thing happens when creating a new .NET 4.6.1 console application in VS 2017 and adding a netstandard2.0 package (e.g. Microsoft.Extensions.Logging.Console).

Heres the diagnostic log of the build: msbuild.log.zip

cc @ericstj @dsplaisted - this is probably an sdk issue?

[ericstj]

It looks like MSBuild is still adding the facades from the targeting pack. I haven't chased down the diff yet, but you should be able to workaround by setting ImplicitlyExpandDesignTimeFacades=false.

[ericstj]

I believe the diff is this: dotnet/msbuild@40cd4d0

Indeed this is an SDK issue.

[ericstj]

Closing here as @dasMulli opened this in the SDK. (thanks!)

[oatkins]

OK, though still a bit stuck about how we'll help those VS2013 users :-(

[ericstj]

We're not stuck, we're just going to fix it in the repo that builds the component that has the problem. @oatkins please follow dotnet/sdk#1539.

[oatkins]

Maybe I misunderstood, but I thought that only helped with vs 2015, not 2013?

…

Sent from my Windows 10 phone From: Eric StJohn<mailto:notifications@github.com> Sent: Friday, August 25, 2017 12:13 PM To: dotnet/standard<mailto:standard@noreply.github.com> Cc: Olly Atkins<mailto:oliverg_atkins@hotmail.com>; Mention<mailto:mention@noreply.github.com> Subject: Re: [dotnet/standard] VS2015/VS2013 build broken when NuGet package is installed using VS2017.3 (#467) We're not stuck, we're just going to fix it in the repo that builds the component that has the problem. @oatkins<https://github.com/oatkins> please follow dotnet/sdk#1539<dotnet/sdk#1539>. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#467 (comment)>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AKa26N-0HU9BOuC0M_ELVAZc9eRu3jDuks5sbvKygaJpZM4PAj6w>.

[ericstj]

The SDK is what's delivering these targets to all versions of VS: 2013/2015/2017. The bug exists because the 2013/2015 msbuild targets didn't handle duplicates during the ImplicitlyExpandDesignTimeFacades target. The workaround here should work for both 2013/2015 and I expect the fix in the SDK to address both as well.

[oatkins]

Wonderful! Thank you.

…

Sent from my Windows 10 phone From: Eric StJohn<mailto:notifications@github.com> Sent: Friday, August 25, 2017 1:14 PM To: dotnet/standard<mailto:standard@noreply.github.com> Cc: Olly Atkins<mailto:oliverg_atkins@hotmail.com>; Mention<mailto:mention@noreply.github.com> Subject: Re: [dotnet/standard] VS2015/VS2013 build broken when NuGet package is installed using VS2017.3 (#467) The SDK is what's delivering these targets to all versions of VS: 2013/2015/2017. The bug exists because the 2013/2015 msbuild targets didn't handle duplicates during the ImplicitlyExpandDesignTimeFacades target. The workaround here should work for both 2013/2015 and I expect the fix in the SDK to address both as well. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#467 (comment)>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AKa26JNYPaJiWfbtcRPUGOVbY7JVSmq7ks5sbwBlgaJpZM4PAj6w>.

[dasMulli]

But I guess a nuget 2.* update would be necessary to know about the ns2.0 => net461 mapping? - at least if you want to add/update packages