[labourcurious]

From https://microsoft.github.io/reactxp/docs/faq

How does ReactXP differ from Xamarin?

Xamarin is a cross-platform solution that allows developers to create apps on iOS, Android and Windows Phone using a single code base. Xamarin apps are written in C# and XAML, allowing .NET developers to leverage their skills and experience. Xamarin apps can be more efficient than React Native apps, which are limited by JavaScript performance and the overhead of the React Native bridge. Xamarin was acquired by Microsoft in early 2016 and is supported by a dedicated team of engineers. It offers a comprehensive development solution including tools for coding, debugging, performance analysis, builds, automated testing, and distribution.

ReactXP, unlike Xamarin, provides a way to create mobile apps and web apps using the same source base. ReactXP (like React and React Native) allow experienced web developers to make use of their existing skills and knowledge. ReactXP was developed by the Skype team at Microsoft in support of their development needs. ReactXP builds upon the work of Facebook and the broader React open source community.

Both Xamarin and ReactXP are great solutions, but they solve somewhat different problems.