I found the answer on another thread here and credit should go to @AxelWass although he did not specifically focus it towards this, it absolutely fixes this issue. The above answer did not.
I had the same issue and solve it by opening the project in a text editor and deleting the following section:
<Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild"> <PropertyGroup> <ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them. For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText> </PropertyGroup> <Error Condition="!Exists('..\packages\Microsoft.Net.Compilers.1.0.0\build\Microsoft.Net.Compilers.props')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\Microsoft.Net.Compilers.1.0.0\build\Microsoft.Net.Compilers.props'))" /> <Error Condition="!Exists('..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.1.0.0\build\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.props')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.1.0.0\build\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.props'))" /> </Target>
Once this is removed, it will resolve this nightmare issue that VS2017 and PM seems to be unable to resolve. I too have run into this multiple times - especially when I blend many projects in the same solutions directory.