.NET for Android error XA0121

Issue

The behavior implemented in the <GetAdditionalResourcesFromAssemblies/> MSBuild task is no longer supported.

This MSBuild task is a precursor to Xamarin.Build.Download that enables downloading of Android packages from the internet.

Libraries using any of the following custom assembly-level attributes will encounter this error:

• IncludeAndroidResourcesFromAttribute
• NativeLibraryReferenceAttribute
• JavaLibraryReferenceAttribute

Solution

The Xamarin Support Libraries, can be simply updated to a newer version on NuGet.

Library authors will need to remove usage of these attributes. Their functionality was removed in .NET for Android 10.2.