.NET 4.6.1/.NET Standard 2.0 build with SGen fails

The context is a .NET Standard 2.0 targeted library Lib. It is referenced by a .NET Framework 4.6.1 targeted library LibNetFramework. (see GitHub repository: https://github.com/emmanuelguerin/issue-sgen)

In LibNetFramework, serialization assemblies generation is forced by the use of the GenerateSerializationAssemblies property set to On. Typically, this would happen when adding a WebReference to the project.

The compilation fails with the message

SGEN : error : An attempt was made to load an assembly with an incorrect format: C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\Microsoft\Microsoft.NET.Build.Extensions\net461\ref\netfx.force.conflicts.dll.

The issue might have been corrected by the use of the patch in https://github.com/dotnet/sdk/pull/1582, that is put ine the LibNetFrameworkPatched project in the GitHub repo.

But this breaks the build, as the netstandard.dll reference is no longer added to the compilation:

LibNetFrameworkPatched\Class1.cs(9,30,9,34): error CS0012: 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'.

You can find an appveyor build failing on the VS2017, and VS2017 preview: https://ci.appveyor.com/project/emmanuelguerin/issue-sgen/build/1.0.6

[mouadhtrabelsi]

I I got this error only in project having web service refrences @tomek14 to fix it i disabled GenerateSerializationAssemblies on teh csproj i added this line for all the build config <GenerateSerializationAssemblies>Off</GenerateSerializationAssemblies>

<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
  <DebugSymbols>true</DebugSymbols>
  <DebugType>full</DebugType>
  <Optimize>false</Optimize>
  <OutputPath>bin\Debug\</OutputPath>
  <DefineConstants>DEBUG;TRACE</DefineConstants>
  <ErrorReport>prompt</ErrorReport>
  <WarningLevel>4</WarningLevel>
  <GenerateSerializationAssemblies>Off</GenerateSerializationAssemblies>
</PropertyGroup>

[joperezr]

I believe we do know now what is happening here. In order for SGen to work correctly on 4.7.1, it will require one of two possible solutions:

• Add binding redirects to it’s config file. (This is the least invasive to your project, but it does mean modifying things inside VisualStudio installation, which might break things once you upgrade to the next version of .NET, so I would advise option 2)
• Add a couple of targets to your .csproj file to make sure we don’t include the design time facades when generating the serialization assemblies. In order to go with this option, simply add the following code right before the </Project> tag.

  <Target Name="RemoveDesignTimeFacadesBeforeSGen" BeforeTargets="GenerateSerializationAssemblies">
    <ItemGroup>
      <ReferencePath Remove="@(_DesignTimeFacadeAssemblies_Names->'%(OriginalIdentity)')" />
    </ItemGroup>
    <Message Importance="normal" Text="Removing DesignTimeFacades from ReferencePath before running SGen." />
  </Target>
 
  <Target Name="ReAddDesignTimeFacadesBeforeSGen" AfterTargets="GenerateSerializationAssemblies">
    <ItemGroup>
      <ReferencePath Include="@(_DesignTimeFacadeAssemblies_Names->'%(OriginalIdentity)')" />
    </ItemGroup>
    <Message Importance="normal" Text="Adding back DesignTimeFacades from ReferencePath now that SGen has run." />
  </Target>