You must add a reference to assembly netstandard errors

[Petermarcu]

@fahadabdulaziz opened this here: microsoft/dotnet#527

Hi,

After targeting .Net Framework 4.7.1, in many projects referencing net standard libraries. I get these errors:

csharp The type 'Object' 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'

Though I all the projects including that targeting net471 are building successfully!

Any thoughts ?

[Petermarcu]

@AlexGhiondea @terrajobst

[juscelior]

Try add netstandard reference in web.config like this:

<system.web> <compilation debug="true" targetFramework="4.7.1" > <assemblies> <add assembly="netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51"/> </assemblies> </compilation> <httpRuntime targetFramework="4.7.1" />

[fahadabdulaziz]

Thank you,
But I'm using WinForms, which mean I don't have web.config.

[fahadabdulaziz]

I managed to fix this problem by adding to csproj file with the references:

<Reference Include="netstandard" />

I don't know if this workaround is good or has side effects, but it silenced the errors for me.

[mbp]

Got the same problem, and the workaround fixes it. But why should this be necessary? Isn't 4.7.1 supposed to implement .NET Standard 2.0?

[fahadabdulaziz]

Just a question, do you have ReSharper installed ?

[mbp]

No

[nandithakw]

I had the same issue with Visual Studio 15.4.4 with net471. Project didn't give errors with net47.
Adding
<ItemGroup> <Reference Include="netstandard" /> </ItemGroup>
as fahadabdulaziz suggested resolves the issue.

[critesjm]

Ran into a similar problem in a project targeting framework 4.6.1 but using newer netstandard memory cache libraries - fixed it with <Reference Include="netstandard" /> but confused about why we need that and/or it's not handled automatically by related tooling.

[danmoseley]

@AlexGhiondea any idea why they are having to add the netstandard reference manually on 471?

[jp2masa]

It was fixed for Visual Studio 15.5: dotnet/msbuild#2567.

[joperezr]

@AlexGhiondea any idea why they are having to add the netstandard reference manually on 471?

This is because in 4.7.1 we no longer have to use the Support package to implicitly add references to facades since netstandard comes inbox starting from 4.7.1. That said, as @jp2masa we had a bug that was fixed in VS15.5 so you no longer have to add this manually.

[plioi]

@joperezr I have VS 15.5.2, and experience the same errors when building from the command line. Visual Studio says there are no errors, but I get these errors from dotnet build.

My problem was that my SDK was pinned to 2.0.3 via global.json, and resolved when pinning to 2.1.2. Strange that VS must be ignoring global.json.