How can I create multiple windows in winui 3.0?

Question

I would like to have a button that creates another window. I'm building off the template app you get in VS2019 Preview So far, I've created a new control BlankWindow, just the default one. I can see that in App::OnLaunched, a window is created with:

window = make<MainWindow>();
window.Activate();

So in my MainWindow.xaml.cs in my button click method, I put:

Window bWindow= make<BlankWindow>();
bWindow.Activate();

That doesn't build, I check the BlankWindow.idl file and see that BlankWindow inherits from Controls and not Windows, so I change it. Now it builds, but when I click the button in the MainWindow, I see the window flicker open and instantly close. What's going on?

Answer 1

Work on multi-window applications is ongoing. It's available as a Preview feature.

https://docs.microsoft.com/en-us/windows/apps/winui/winui3/#preview-features

Answer 2

You can find the solution to this problem in the definition of the Window Class for the Windows UI Library (WinUI) under the subtitle "Create a new Window on a new thread". To put the section in context it would help to read the entire webpage. It's not that long.