COMException (0x8000FFFF): Fatal error (0x8000FFFF (E_UNEXPECTED))

[SchreinerK]

Nothing indicates what causes the exception and the exception is also not very helpful.

Reproduce

<Shell
    x:Class="Issue220611_1_Maui_DockLayout.AppShell"
    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:local="clr-namespace:Issue220611_1_Maui_DockLayout"
    xmlns:mauipane="clr-namespace:MauiPane;assembly=MauiPane"
    Shell.FlyoutBehavior="Disabled">

    <ShellContent>
        <ContentPage>
            <ScrollView>
                <VerticalStackLayout>
                    <mauipane:DockLayout>
                        <Label Text="Name"/>
                        <Label Text="Value"/>
                    </mauipane:DockLayout>
                    <mauipane:DockLayout>
                        <Label Text="Name"/>
                        <Label Text="Value"/>
                    </mauipane:DockLayout>
                </VerticalStackLayout>
            </ScrollView>
        </ContentPage>
    </ShellContent>
</Shell>

Solution

in MauiProgram.cs call MauiPane.Hosting.ConfigureMauiPane

using MauiPane.Hosting;

namespace Issue220611_1_Maui_DockLayout;

public static class MauiProgram {

    public static MauiApp CreateMauiApp() {
        var builder = MauiApp.CreateBuilder();
        builder
            .UseMauiApp<App>()
            .ConfigureMauiPane()
            ...
        return builder.Build();
    }

}

There should be an info.txt opened like in CommunityToolkit.Maui I found it only by chance in MauiPane.Gallery and then later in Issues when I wanted to report the error.