正确的UWP AppWindow上的ContentDialog

Question

I am experimenting with the new AppWindow that came with the Windows 10 1903 update for creating multi-windowed UWP applications that use same UI-thread.

I am having an issue where I cannot get a ContentDialog to be modal on the second window. Microsoft's documentation states the following: "MessageDialog will not be modal to the correct window, recommendation is to use ContentDialog instead." However, it is not explained how this is achieved...

Source: https://docs.microsoft.com/en-us/uwp/api/windows.ui.windowmanagement.appwindow

Would anyone know how the get the ContentDialog to be modal on the correct Window?

Answer 1

Thank you for reporting this, we will fix the documentation for ContentDialog.

To open the ContentDialog on the correct window, you'll need to set the ContentDialog's XamlRoot property to the same XamlRoot as an element in the AppWindow.

noWifiDialog.XamlRoot = elementAlreadyInTheAppWindow.XamlRoot;

Note that there is also a known limitation where only one ContentDialog can be open per thread at a time - meaning the app can't show a modal dialog in two windows on the same thread. In this scenario, opening the second dialog will throw an exception which you'll need to try/catch.

The WinUI bug: Only one ContentDialog can be open per thread (even with multiple AppWindows) #794