Failed to apply binding to property [DependencyPropertyDetails(Source)] on [Microsoft.UI.Xaml.Controls.Image]

[HakanL]

How can I troubleshoot and fix this error I get after upgrading to Uno SDK 5.3 (from multi-head 5.1)? This is the error:
Failed to apply binding to property [DependencyPropertyDetails(Source)] on [Microsoft.UI.Xaml.Controls.Image] (ImageSourceConverter cannot convert from DMXCore.DMXCore100.Models.MenuItem.)
Call stack:

System.NotSupportedException: ImageSourceConverter cannot convert from DMXCore.DMXCore100.Models.MenuItem.
   at System.ComponentModel.TypeConverter.GetConvertFromException(Object value)
   at System.ComponentModel.TypeConverter.ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, Object value)
   at Microsoft.UI.Xaml.Media.ImageSourceConverter.ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, Object value) in /__w/1/s/src/Uno.UI/UI/Xaml/Media/ImageSourceConverter.cs:line 62
   at Uno.UI.DataBinding.BindingPropertyHelper.ConvertUsingTypeDescriptor(Type type, Object value) in /__w/1/s/src/Uno.UI/DataBinding/BindingPropertyHelper.cs:line 1345
   at Uno.UI.DataBinding.BindingPropertyHelper.Convert(Type propertyType, Object value) in /__w/1/s/src/Uno.UI/DataBinding/BindingPropertyHelper.cs:line 1389
   at Microsoft.UI.Xaml.Data.BindingExpression.SetTargetValueSafe(Object v, Boolean useTargetNullValue) in /__w/1/s/src/Uno.UI/DataBinding/BindingExpression.cs:line 700

Note that the DMXCore.DMXCore100.Models.MenuItem is my class object, it's just a class that has properties (like title, icon/avatar, etc) for a menu displayed in a WrapPanel with Uno Cards. I don't bind the class to any property, but I'm binding the Avatar Icon on the Card to a string property in that class that has the path of the icon to display. I didn't get these errors in earlier versions, but also, everything is working, the icons are displayed, and if I remove the binding then the error goes away (and also the icon). Unfortunately my project is fairly complex so it's not trivial to create a sample to reproduce this, I'm initially hoping someone can point me in the right direction of how I can troubleshoot the source of this error, and come up with a fix.

[MartinZikmund]

@HakanL can you please send a snippet of that relevant part of XAML that includes the binding? Also - it might be interesting to attach to DataContextChanged to see which layer gets set to that specific instance

[HakanL]

Simple repro repo: https://github.com/HakanL/UnoApp10
I get the errors both on my RPi 4 device, and in WSL2 on my Windows dev machine. Appreciate any insight!

[jeromelaban]

@kazo0 the issue seems to come from MaterialAvatarOutlinedCardStyle:

uno.toolkit.ui/src/library/Uno.Toolkit.Material/Styles/Controls/v1/Card.xaml

Line 509 in 57206f4

Value="{StaticResource DefaultAvatarContentTemplate}" />

And this is:

uno.toolkit.ui/src/library/Uno.Toolkit.Material/Styles/Controls/v1/Card.xaml

Lines 61 to 65 in 57206f4

	<DataTemplate x:Key="DefaultAvatarContentTemplate">
	<Image Source="{Binding}"
	Stretch="Uniform"
	MaxHeight="40" />
	</DataTemplate>

Where the binding does not seem to be changing its path in any way.

[kazo0]

@jeromelaban Seems that we need to avoid allowing the DataContext to be inherited for the XContent and XContentTemplate properties in the Card.

Similar to how it's done by ContentControl: https://github.com/unoplatform/uno/blob/0cf4db7ec540adb2942f42943790f638bad6cde3/src/Uno.UI/UI/Xaml/Controls/ContentControl/ContentControl.cs#L100-L106

Not sure if we would be able to do the same thing in Toolkit? Since FrameworkPropertyMetadata is an Uno-only thing right?

But I'm a little confused because we are forwarding these properties to the inner ContentPresenter:

uno.toolkit.ui/src/library/Uno.Toolkit.Material/Styles/Controls/v2/Card.xaml

Lines 649 to 659 in 57206f4

	<!-- Avatart part -->
	<ContentPresenter
	x:Name="AvatarContentPresenter"
	Margin="16,0,0,0"
	HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
	VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
	AutomationProperties.AccessibilityView="Raw"
	Content="{TemplateBinding AvatarContent}"
	ContentTemplate="{TemplateBinding AvatarContentTemplate}"
	IsHitTestVisible="False"
	Visibility="{Binding AvatarContent, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource EmptyOrNullToCollapsedConverter}}" />

So I would have though that the ContentPresenter would properly set its ContentTemplate's DataContext to Content

[MartinZikmund]

Yes, I would expect the DataContext in the template to correctly be the Content - when both Content and ContentTemplate are specified, the ContentPresenter should use the template to display the Content, which is then used as the DataContext of the template. I would expect the same works correctly in WinUI, right? Did this work in previous versions of Uno? If yes, then it might be a regression

[Xiaoy312]

@kazo0 you can do so:

		public static DependencyProperty TestProperty { get; } = DependencyProperty.Register(
			nameof(Test),
			typeof(string),
			typeof(UnreleatedTestClassForOtherThing),
#if !HAS_UNO
			new PropertyMetadata(default(string))
#else
			new FrameworkPropertyMetadata(default(string), FrameworkPropertyMetadataOptions.ValueDoesNotInheritDataContext | FrameworkPropertyMetadataOptions.AffectsMeasure)
#endif
		);