[WinUI] ItemsSource="ABCD" or ItemsSource="1234" throwing XamlParseException

[agneszitte]

Describe the bug

Using ItemsSource="ABCD" or ItemsSource="1234" for example as a quick ItemsSource during tests, throw a XamlParseException on WinUI. (As opposed to building fine on UWP)

Exception thrown: 'Microsoft.UI.Xaml.Markup.XamlParseException' in WinRT.Runtime.dll
WinRT information: Failed to assign to property 'Microsoft.UI.Xaml.Controls.ItemsControl.ItemsSource'. [Line: 16 Position: 17]
XAML parsing failed.

Steps to reproduce the bug

Try this snippet of code in a WinUI app:

	<StackPanel>
		<ItemsControl ItemsSource="ABCDEFG" />
		<ComboBox ItemsSource="ABCDEFG" />
		<ItemsControl ItemsSource="123456" />
		<ComboBox ItemsSource="123456" />
		<ItemsControl ItemsSource="@#$%?!" />
		<ComboBox ItemsSource="@#$%?!" />
	</StackPanel>

• WinUI Sample App: TestComboBoxWinUIOnly.zip
• UWP Sample App (to compare): TestComboBoxUWPOnly.zip

Expected behavior

There should be no XamlParseException like for UWP

Screenshots

No response

NuGet package version

WinUI 3 - Windows App SDK 1.3.3: 1.3.230724000

Windows version

Windows 10 (21H2): Build 19044

Additional context

I did not find a similar issue opened so I added this one. This is really useful to have on hand for quick tests.

[brabebhin]

As long as there's a readable error in the output this is actually fine - such a situation is obviously bogus and should be hunted down. One of the annoying parts of UWP was having to track down such weird XAML lines (usually typos) when things suddenly stopped working.

[JesseCol]

Thanks! This is currently by-design.