WinUI in Desktop app is silently crashed if I put Grid descendant to the Grid.Children collection

Hello!

I created a "Blank App, Packaged (WinUI in Desktop) from VS templates.

In MainPage.xaml I set a name for the root grid.

<Grid x:Name="RootGrid"> </Grid>

Next, in MainPage.xaml.cs, I created a Grid descendant and put it to the Children collection of the RootGrid.

public sealed partial class MainWindow : Window { public MainWindow() { this.InitializeComponent(); RootGrid.Children.Add(new MyGrid() { Background = new SolidColorBrush(Colors.Red) }); } } public class MyGrid : Grid { }

The main window shows for a seconds and application exits without any errors or exceptions.

Version Info

NuGet package version: Microsoft.WinUI 3.0.0-preview2.200713.0 Windows 10 version: 1903 (OS Build 18362.1082)

[stevenbrix]

@PureWeen and @BorzillaR, I just validated that the attached repro app no longer has an issue with preview3

[stevenbrix]

@BorzillaR - I’m closing this out now that preview3 has been released. Please respond if you are still experiencing this issue.