问题
I have a problem with these packages which I wanted to use on my Xamarin form using .net standard 2.0
Package 'ExifLib.PCL 1.0.1' was restored using '.NETFramework,Version=v4.6.1' instead of the project target framework '.NETStandard,Version=v2.0'. This package may not be fully compatible with your project.
Package 'Microsoft.Bcl 1.1.6' was restored using '.NETFramework,Version=v4.6.1' instead of the project target framework '.NETStandard,Version=v2.0'. This package may not be fully compatible with your project.
Package 'Microsoft.Bcl.Async 1.0.165' was restored using '.NETFramework,Version=v4.6.1' instead of the project target framework '.NETStandard,Version=v2.0'. This package may not be fully compatible with your project.
Package 'Mobilist.AdvancedTimer.Forms.Plugin 1.0.1' was restored using '.NETFramework,Version=v4.6.1' instead of the project target framework '.NETStandard,Version=v2.0'. This package may not be fully compatible with your project.
Package 'PCLStorage 1.0.2' was restored using '.NETFramework,Version=v4.6.1' instead of the project target framework '.NETStandard,Version=v2.0'. This package may not be fully compatible with your project.
Package 'Rg.Plugins.Popup 1.0.4' was restored using '.NETFramework,Version=v4.6.1' instead of the project target framework '.NETStandard,Version=v2.0'. This package may not be fully compatible with your project.
Does that mean I can't use this library any more?
回答1:
Does that mean I can't use this library any more?
No, you should be able to use nearly all libraries that are PCL spec compliant inside of a .NET Standard 2.0 class library. You can checkout the .NET documentation to see list of PCL profiles with their supported platform and their corresponding .NET Standard supported version.
Package warning explanation
With .NET Standard 2.0 and the updated tooling in .NET Core SDK 2+ the .NET team wanted to make it easier to update or make use of .NET Standard libraries. The issue is that not all NuGet packages have been updated to support a version of .NET Standard. So they introduced a fallback targeting .NET Framework 4.6.1 which is nearly 100% compliant with .NET Standard (There are some API that are in the .NET Standard 2.0 spec that are not in .NET Framework 4.6.1 but they can be brought in via NuGet packages if required). So the warning you see is to inform you that the packages do not conform to a .NET Standard version you are targeting and as such may contain API's that are not executable in your runtimes making use of your .NET Standard 2.0 library.
Once you have tested that everything is working as expect you can add the NoWarn="NU1701" to your PackageReference in your csproj which will remove the warning. One thing to note adding NoWarn="NU1701" to a individual package does not remove the warning for dependencies. To remove those warning you must either include them as PackageReferences (via NuGet) or ignore NU1701 warning at a project level.
If you run into fallback issues you can adjust the target framework fallback via overriding the AssetTargetFallback in your csproj to something like:
<AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wpa81;</AssetTargetFallback>
来源：https://stackoverflow.com/questions/47782611/xamarin-form-does-this-give-limitation-access-the-libraries