The ContentDialog.ShowAsync throws the ArgumentException

Describe the bug Hi, the ShowAsync throws the ArgumentException Value does not fall within the expected range.

Steps to reproduce the bug

    public sealed partial class MainWindow : Window {
        public MainWindow() {
            this.InitializeComponent();
        }

        private async void myButton_Click(object sender, RoutedEventArgs e) {
            var dlg = new ContentDialog() {
                Title = "Result Dialog",
                Content = "Test",
                CloseButtonText = "OK"
            };
            await dlg.ShowAsync();
        }
    }

<StackPanel x:Name="stackPanel" Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center">
        <Button x:Name="myButton" Click="myButton_Click">Click Me</Button>
</StackPanel>

Expected behavior

Screenshots

Version Info

NuGet package version:

[WinUI 3 - Project Reunion 0.5: 0.5.5]

Windows app type:

UWP	Win32
	Yes

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
October 2020 Update (19042)	Yes
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context

 	WinRT.Runtime.dll!WinRT.ExceptionHelpers.ThrowExceptionForHR(int hr = -2147024809)	Unknown
 	Microsoft.WinUI.dll!ABI.Microsoft.UI.Xaml.Controls.IContentDialog.Microsoft.UI.Xaml.Controls.IContentDialog.ShowAsync()	Unknown
 	Microsoft.WinUI.dll!Microsoft.UI.Xaml.Controls.ContentDialog.ShowAsync()	Unknown
>	App2.dll!App2.MainWindow.myButton_Click(object sender = {Microsoft.UI.Xaml.Controls.Button}, Microsoft.UI.Xaml.RoutedEventArgs e = {Microsoft.UI.Xaml.RoutedEventArgs}) Line 34	C#
 	[Lightweight Function]	
 	Microsoft.WinUI.dll!ABI.Microsoft.UI.Xaml.RoutedEventHandler.Do_Abi_Invoke.AnonymousMethod__0(Microsoft.UI.Xaml.RoutedEventHandler invoke = {Method = <Internal Error evaluating expression>})	Unknown
 	WinRT.Runtime.dll!WinRT.ComWrappersSupport.MarshalDelegateInvoke<Microsoft.UI.Xaml.RoutedEventHandler>(System.IntPtr thisPtr = 0x186fbdac, System.Action<Microsoft.UI.Xaml.RoutedEventHandler> invoke = {Method = {System.Reflection.RuntimeMethodInfo}})	Unknown
 	Microsoft.WinUI.dll!ABI.Microsoft.UI.Xaml.RoutedEventHandler.Do_Abi_Invoke(System.IntPtr thisPtr = 0x186fbdac, System.IntPtr sender = 0x100a23ec, System.IntPtr e = 0x1a430628)	Unknown

[StephenLPeters]

@sylveon is correct, the best work around it to parent the content dialog somewhere in your xaml tree, preferably from markup.

[sylveon]

An alternative is putting the ContentDialog directly in the XAML code, then the XamlRoot is automatically assigned and as a bonus localization is easier since resw just works.