.NET Core 3 using WinUI

Question

With .NET Core 3 in preview, it is possible to create a WinForms or WPF "desktop application" on the .NET Core platform.

Using XAML islands, it is possible to host UWP controls in a WPF application.

Does .NET Core 3 and up directly support the WinUI library? Or is the best practice to start from a WPF application and host the controls (NavigationView etc ...)?

UPDATE

dotnet new winforms and dotnew new wpf will create .net core projects for their respective technologies.

Is the intention (or is it already possible, and if so: how) to also support something like dotnet new uwp, where UWP style controls are "the default" (by referencing the WinUI library) instead of starting from WPF and using XAML islands.

Answer 1

.NET Core 3 allows you to include the Windows Desktop SDK that contains that WinForms and WPF frameworks. This SDK is not cross-platform, only works on Windows.

XAML Islands v1 allows to host UWP XAML controls in WPF and WinForms in .NET Framework and .NET Core 3. However, in .NET Framework, only the UWP XAML controls that come with the OS are supported. .NET Core 3 doesn't have this limitation; you can host 3rd party controls, regardless are managed (e.g., written in C#) or native (e.g. written in C++/WinRT).

WinUI 2 is a library of UWP controls created by the UWP XAML team too. The quality of these controls is the same as the inbox OS controls. The WinUI 2 controls aren't bound to the latest Windows 10 version (as happening with the inbox OS controls), they run on the 1703 build and above (downlevel support). You can use these WinUI 2 controls inside of a XAML Island in WinForms or WPF .NET Core 3, and not with the .NET Framework so far.

Last but not least, XAML Islands v1 only works on the Windows 10 1903 update, even if the content of the island works on older OS versions.

Some links:

• Xaml Islands v1 Updates and Roadmap

• Host a custom UWP control in a WPF app using XAML Islands

Answer 2

XAML Islands should be normally supported in .NET Core 3 based WPF app. The difference here is just the runtime platform - normally WPF apps run on top of full .NET Framework, now it is possible to run them on .NET Core 3 as well.

If it does not work, report the issue on WinUI GitHub or CoreFX GitHub. Keep in mind .NET Core 3 is in its first public preview, so this scenario is probably not fully tested yet.