"dotnet build" failed with error NETSDK1073 for the .NET core 3.0 app with reference to a .NET Standard 2.1 class lib

Steps to reproduce

1. Install .NET core sdk 3.0.100-preview6-012012
2. Create a .NET core 3.0 app with reference to a .NET Standard 2.1 class lib with below CLI dotnet new console -o consoleapp30 dotnet new classlib -n CSNS21Lib -f netstandard2.1 dotnet add reference …\CSNS21Lib\CSNS21Lib.csproj
3. run “dotnet build” to observe the result

##Note

1. This issue also repro with VS
2. This issue is not repro on the .NET core 3.0 app with reference to a .NET Standard 2.0 class lib

Expected behavior

The project can be built successfully

Actual behavior

Build with error NETSDK1073: The FrameworkReference ‘NETStandard.Library’ was not recognized

Environment data

dotnet --info output: .NET Core SDK (reflecting any global.json): Version: 3.0.100-preview6-012012 Commit: 94b54a5ef6

Runtime Environment:
OS Name: Windows OS Version: 10.0.17763 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\3.0.100-preview6-012012\

Host (useful for support): Version: 3.0.0-preview6-27718-08 Commit: 7c7a2e9074

.NET Core SDKs installed: 2.1.800-preview-009677 [C:\Program Files\dotnet\sdk] 2.2.400-preview-010195 [C:\Program Files\dotnet\sdk] 3.0.100-preview6-012012 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed: Microsoft.AspNetCore.All 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.0.0-preview6-19265-03 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.NETCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 3.0.0-preview6-27718-08 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.WindowsDesktop.App 3.0.0-preview6-27718-08 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET Core runtimes or SDKs: https://aka.ms/dotnet-download

[dsplaisted]

As a workaround, you can put the following in your .NET Core project which references .NET Standard 2.1:

  <Target Name="WorkaroundNetStandard" AfterTargets="ResolvePackageAssets">
    <ItemGroup>
      <TransitiveFrameworkReference Remove="NETStandard.Library" />
    </ItemGroup>
  </Target>

[Fabi]

This is working using the latest VS build and the latest preview6 CLI.

@livarcocc - Specifically which versions? I still get this error with the following versions:

NetCoreApp3.0: preview6-27804-01 Visual Studio: 16.1.3

You have to use the latest Visual Studio preview.