如果不需要，建议移除net standard类库中的Microsoft.NETCore.Portable.Compatibility

使用Microsoft.NETCore.Portable.Compatibility会破坏该类库在Mono和Xamarin平台的兼容性

可能导致的问题

provides a compile-time reference assembly for mscorlib on MonoAndroid,Version=v6.0, but there is no run-time assembly compatible with win.

error CS1703: Multiple assemblies with equivalent identity have been imported

和

无法安装程序包“Microsoft.NETCore.Jit 1.0.2”