问题
I'm trying to make Npgsql, the PostgreSQL provider for .NET, available for consumption by Xamarin users. Npgsql already supports the .NET Platform Standard (version 3), and the documentation on the standard contains the following sentence:
If a library targets .NET Platform Standard version 1.3, it can only run on .NET Framework 4.6 or later, .NET Core, Universal Windows Platform 10 (UWP), and Mono/Xamarin platforms.
I can successfully install the Npgsql nuget from my Xamarin.Android project. However, when I try to build I get the following error:
System.IO.FileNotFoundException: Could not load assembly 'System.Security.Cryptography.Algorithms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. Perhaps it doesn't exist in the Mono for Android profile?
Now, that packages (like many RC2 packages Npgsql depends on) has a lib/MonoAndroid10 directory containing . (also the same in ref), which seems to indicate that the package is supported on Mono.Android, but no DLL is necessary (since the logic is part of the framework). That's great, but the Xamarin.Android build process includes a ResolveAssemblies task, which walks the DLL dependency graph (this is the relevant code). Since Npgsql's netstandard13 DLL references System.Security.Cryptography.Algorthims.dll, this fails.
I'm confused that the nuget declares "it's all good", while the build process itself seems obviously incompatible with consuming netstandard13 dependencies.
Any ideas?
来源：https://stackoverflow.com/questions/37484894/consuming-netstandard13-packages-from-xamarin-projects