Xamarin
Xamarin. Forms is an open source mobile UI framework from Microsoft for building iOS, Android, & Windows apps with . NET from a single shared codebase. Whether you want a consistent look across platforms or prefer native look and feel, Xamarin. Forms will get you up and running in no time.

Advantages :
- Native User Experience: Xamarin has full access to native APIs and toolkits used on Android, iOS and Windows platforms. Consequently, it can provide native (or near-native) design and performance for every application.
- Single Technological Stack: One of the main pros of Xamarin cross-platform application development is that a single language C# creates all kinds of solutions. Moreover, there’s no need to switch between environments — you can do everything in Visual Studio. This is convenient and time-effective because developers perform the same process using one language instead of two different languages. Hence, Xamarin is easy to learn.
- Shareable Code: Xamarin is often referred to as a “write once, use everywhere” development platform because it creates a 60-95% reusable code. A single codebase can run on various platforms providing native performance and may require slight changes only.
- Time and Costs Saving: A sharable codebase and a single technological stack save time spent on the development cycle. You code once and then can reuse most of this code for other solutions, making only slight adjustments and not spending time on the same procedure. This means you can release your product faster.
- Simplified Maintenance: It is remarkably easy to maintain apps developed with Xamarin.Forms as they share code. If you need to update applications and fix some issues, just do it in the source code, and all changes will be automatically applied to other solutions. Again, it saves time, developer involvement and finances.
- Testing: The platform offers comprehensive solutions to test and monitor application performance and UI – Xamarin Test Cloud and Xamarin Test Recorder.
- Technical Support by Microsoft: Xamarin guarantees stability, continuous technical backing and fast issue resolution because Microsoft — one of the world’s leading tech software companies, supports this platform.