Add a reference to assembly netstandard error with .NET Framework 4.6.1 project

Question

A
.NET Framework 4.6.1
project which has a reference to a nuget package built with
.netstandard2.0
is no more building. The following is the error. It is around the time when the IT Department uninstalled
.net core 2.0 SDK
from the build machine.

I added
<Reference Include="netstandard" />
to the project. The following error goes away but gives another error.

How can I fix this problem? Will installing
.net core 3.1 SDK
solve the problem?

"c:/Program Files (x86)/Microsoft Visual Studio/2019/BuildTools/MSBuild/Current/Bin/msbuild.exe" /p:Configuration=Release /verbosity:quiet /p:Platform="x86" /clp:ErrorsOnly /nologo /noautorsp /m

26-Apr-2022 18:13:55 C:\bamboo6104\xml-data\build-dir\BAM-PF1818-JOB1\MyProject\Services\SubscriptionProvider.cs(37,41): 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'. [C:\bamboo6104\xml-data\build-dir\BAM-PF1818-JOB1\MyProjectFolder\MyProject.csproj]

Answer 1

.net framework 4.6.1 does not fully support .netstandard 2.0. most likely your nuget package got updated. as 4.6.1 is out of support, so you should upgrade to 4.8 in any event. .net 4.8 has complete support of .netstandard 2.0

.net 3.1 will be out of support in December, so you might as well install .net 6 if you want to create and build .netstandard 2.0 libraries.