XamarinForms

Xamarin.Forms is a cross-platform UI toolkit that enables developers to build native user interfaces for iOS, Android, and Windows from a single shared C# codebase. UI can be defined in XAML or in C#, and the shared project is complemented by platform-specific projects to host the rendered UI.

First released by Xamarin in 2014 and later acquired by Microsoft in 2016, Xamarin.Forms integrates with Visual Studio and other .NET tooling. It uses a renderer architecture where cross-platform controls are mapped to native controls on each platform, providing a native look and feel. The framework includes a library of common controls, layouts, navigation primitives, and supports data binding and MVVM patterns.

Key features include a broad set of shared controls (such as Button, Label, Entry, ListView, and CollectionView), layout containers (like StackLayout, Grid, and FlexLayout), and navigation. UI can be constructed in XAML or C#, and developers can extend functionality through custom renderers to access platform-specific features or optimize performance. Data binding, styles, theming, and platform-aware behavior are supported to facilitate responsive, maintainable apps.

Relation to .NET MAUI and status: Xamarin.Forms is considered the predecessor to .NET MAUI, which provides a more unified single-project experience and updated APIs. Microsoft continues to provide maintenance releases for existing Xamarin.Forms apps, but MAUI is encouraged for new cross-platform projects, reflecting a shift in the .NET cross-platform strategy.