Building ASP.NET-Core 3.1 with .NET-Standard 2.0 projects leads to conflicting Microsoft.AspNetCore.Mvc.Analyzers assemblies

Question

I'm trying to build an ASP.NET-Core 3.1 (netcoreapp3.1) application which has a dependency on a NuGet library that is .NET-Standard 2.0 which uses MSBuild SDK "Microsoft.NET.Sdk.Razor".

This builds and runs fine from Visual Studio (2019) but when I run dotnet build I get the following error:

Build FAILED.

CSC : error CS8034: Unable to load Analyzer assembly 
 C:\Users\daniel\.nuget\packages\microsoft.aspnetcore.mvc.analyzers\2.2.0\analyzers\dotnet\cs\Microsoft.AspNetCore.Mvc.Analyzers.dll
 : Assembly with same name is already loaded [D:\git\myapp\src\myapp.App\myapp.App.csproj]
    0 Warning(s)
    1 Error(s)

My guess is that my .NET-Standard 2.0 library is pulling in Microsoft.CodeQuality.Analyzers 2.x via the Microsoft.NET.Sdk.Razor SDK and this conflicts with the one being pulled in by the ASP.NET-Core 3.1 application.

Questions:

1. Is there either a way to build my application via command line in the same way Visual Studio does it?

2. Is the proper solution to use multi-targeting and #if NETCOREAPP3_1 blocks in my library?

Answer 1

This is a workaround to hide the annoying message, but it will not actually remove the underlying issue:

Edit the .csproj and add a 8034 (CS8034) <NoWarn> to the Configuration/Platform <PropertyGroup> like this:

<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <TargetFramework>net5.0</TargetFramework>
    <!-- ... -->
  </PropertyGroup>

  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
    <NoWarn>8034</NoWarn>
  </PropertyGroup>

  <!-- ... -->
</Project>