问题
Severity Code Description Project File Line Suppression State Error Could not install package 'Xamarin.Android.Support.v4 28.0.0.3'. You are trying to install this package into a project that targets '.NETPortable,Version=v4.5,Profile=Profile78', but the package does not contain any assembly references or content files that are compatible with that framework. For more information, contact the package author.
回答1:
If Manage Packages is for Forms project , can not install Xamarin.Android.Support.v4 nuget package .(AppEntryTest is name of my project)
You need to open Manage Packages for Solution (Right click solution -> select Manage Nuget Packages for solution..)
then can install as follow :
来源：https://stackoverflow.com/questions/62209173/i-tried-to-install-xamarin-android-support-v4-on-xamarin-project-but-it-shows-er