In projects targeting .NET 4.7, the net451 assembly is resolved

[alastairs]

When including Serilog.Settings.Configuration 3.0.0-dev in a .NET Framework 4.7.1 (net471) project, NuGet resolves the net451 assembly from the package instead of the netstandard2.0 assembly. This pulls in Microsoft.Extensions.Options.ConfigurationExtensions >= 1.1.2 rather than >= 2.0.0 as defined in the netstandard2.0 assembly. This causes a package conflict in our solution with another project that requires v2.0 of that package. NuGet resolves this dependency to v1.1.2:

There was a conflict between "Microsoft.Extensions.Options.ConfigurationExtensions, Version=1.1.2.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" and "Microsoft.Extensions.Options.ConfigurationExtensions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60".
    "Microsoft.Extensions.Options.ConfigurationExtensions, Version=1.1.2.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" was chosen because it was primary and "Microsoft.Extensions.Options.ConfigurationExtensions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" was not.
    References which depend on "Microsoft.Extensions.Options.ConfigurationExtensions, Version=1.1.2.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" [C:\Users\AlastairSmith\.nuget\packages\microsoft.extensions.options.configurationextensions\1.1.2\lib\netstandard1.1\Microsoft.Extensions.Options.ConfigurationExtensions.dll].
        C:\Users\AlastairSmith\.nuget\packages\microsoft.extensions.options.configurationextensions\1.1.2\lib\netstandard1.1\Microsoft.Extensions.Options.ConfigurationExtensions.dll
        Project file item includes which caused reference "C:\Users\AlastairSmith\.nuget\packages\microsoft.extensions.options.configurationextensions\1.1.2\lib\netstandard1.1\Microsoft.Extensions.Options.ConfigurationExtensions.dll".
            C:\Users\AlastairSmith\.nuget\packages\microsoft.extensions.options.configurationextensions\1.1.2\lib\netstandard1.1\Microsoft.Extensions.Options.ConfigurationExtensions.dll
    References which depend on "Microsoft.Extensions.Options.ConfigurationExtensions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" [].
        F:\code\platform\src\ServiceHost\bin\Debug\netstandard2.0\CH360.Platform.ServiceHost.dll
        Project file item includes which caused reference "F:\code\platform\src\ServiceHost\bin\Debug\netstandard2.0\CH360.Platform.ServiceHost.dll".
            F:\code\platform\src\Queue.Rabbit\bin\Debug\netstandard2.0\CH360.Platform.Queue.Rabbit.dll
            F:\code\platform\src\ServiceHost\bin\Debug\netstandard2.0\CH360.Platform.ServiceHost.dll

[MV10]

Interestingly, there seems to be a NuGet issue about the exact opposite problem, a net471 project that picks up the netstandard2.0 but they don't want it to: https://github.com/NuGet/docs.microsoft.com-nuget/issues/880

If your issue could be fixed by NuGet packaging changes, I assume it would create the opposite problem for others. Sounds pretty thorny (but I'm not exactly a NuGet packaging expert).