Updating an Uno application to WinUI 3.0

Uno Platform supports authoring apps using WinUI 3's API. This article details the changes required when migrating an application from the UWP API set to the WinUI 3 API set.

Migrating an app to WinUI 3.0

NuGet updates:
- Uno.UI becomes Uno.WinUI
- Uno.UI.DevServer becomes Uno.WinUI.DevServer
- Uno.UI.Lottie becomes Uno.WinUI.Lottie
- Uno.UI.Foldable becomes Uno.WinUI.Foldable
String replacements:
- Windows.UI.Xaml becomes Microsoft.UI.Xaml
- Windows.UI.Composition becomes Microsoft.UI.Composition
Update App.xaml.cs:
- If your solution was created with an older version of the Uno app template, you'll need to update App.xaml.cs for compatibility with WinUI 3/Project Reunion.
```
Fixes to apply:
```
  - Ensure Window doesn't fall out of scope (diff)
  - Fix invalid defines (diff)

API Changes

Changed or removed controls

MapControl is missing
MediaPlayerElement is missing
WebView is now WebView2

For a full list of unavailable controls and visual features, as well as timelines for restoration in some cases, consult the WinUI 3 Feature Roadmap.

WinRT API changes for Desktop apps

Some WinRT APIs are unsupported in WinUI 3 Desktop apps, notably CoreDispatcher, CoreWindow, and ApplicationView. Consult this guide for supported alternatives to those APIs. DispatcherQueue, the replacement for CoreDispatcher in WinUI 3, is supported by Uno Platform.

Creating an application from the templates

Instructions are available in Getting started with WinUI 3 for creating a new Uno Platform application targeting WinUI 3.