Framework · 2011–2022 · Cloud Scale
Xamarin
C# for iOS and Android before Flutter and React Native won the cross-platform narrative.
Why Xamarin faded
Xamarin faded because mobile UX demands native-feeling tooling and Microsoft eventually bet on MAUI and acquired alternatives. Shared business logic could not save heavyweight UI abstractions. Cross-platform stuck; Xamarin specifically did not.

Compare with
Related
Language · 2000–now
C# / .NET
Microsoft's managed stack grew up — cross-platform, open source, and still dominant in enterprise Windows shops.
Framework · 2017–now
Flutter
Paint your own pixels on iOS and Android from one codebase. Google's bet against native UI fragmentation.
Framework · 2015–now
React Native
React components on native views. Share logic with web until platform differences ruin your sprint.