XamlC warning XC0045: Binding: Property "BindingContext" for Source={RelativeSource TemplatedParent}

[LeoJHarris]

Hi all I've enabled the following in .csproj so we can improve app performance following this link:

<!--# Enables XAML Compilation with Source Generation for MAUI -->
<MauiEnableXamlCBindingWithSourceCompilation>true</MauiEnableXamlCBindingWithSourceCompilation>

<!--# Treats the specified warning as an error -->
<WarningsAsErrors>$(WarningsAsErrors);XC0022</WarningsAsErrors>

I would like to know how to deal with these situations in XAML as we have a few of them scattered through our XAML files:

BindingContext="{Binding BindingContext, Source={RelativeSource TemplatedParent}}"

I am getting the following error:

XamlC warning XC0045: Binding: Property "BindingContext" not found on "Microsoft.Maui.Controls.Xaml.NullExtension".

And am wondering how we are meant to set the x:DataType for Source={RelativeSource TemplatedParent}?

[vitek-karas]

@simonrozsival @StephaneDelcroix

[BurningLights]

You can set the x:DataType within a Binding statement So, whatever type the ControlTemplate is applied to, it would be like BindingContext=“{Binding BindingContext, Source={RelativeSource TemplatedParent}, x:DataType={x:Type blah}}”.

[LeoJHarris]

@simonrozsival see the following repo here:

You can switch between Debugand MethosfRelease configuration which is just a custom name for a release build we use.

https://github.com/LeoJHarris/CompiledBinding_DataType_Broken.git

[simonrozsival]

I have a few observations:

• when I build the app, I don't get any warning from XamlC
• when I build and run the app in the MethosfRelease configuration, it crashes at startup
• when I rename MethosfRelease to the "standard" Release, the app starts correctly and I can see that the icons displayed in those buttons are different from the ones displayed in Debug configuration
• when inspecting the IL produced by XamlC, the bindings for those image sources are compiled correctly:

- even when I disable `MauiEnableXamlCBindingWithSourceCompilation`, I'm still seeing other images than the ones specified in the binding source.

I'm fairly confident the problem is not related to MauiEnableXamlCBindingWithSourceCompilation and the way you're using your bindings and the x:DataType you're using. There might be something else wrong with the way the embedded resources are bundled into the app and used at runtime.

• I am not sure what your reasons to use the MethodsfRelease configuration, but I think the app build is not behaving as you expect because of it and it is skipping some important steps that it does only in Release configuration.

My conclusion is that you're not running into issues with compiled bindings. You might want to open a new issue where you describe the problem with the embedded resources you're having.

[LeoJHarris]

@simonrozsival I was also running into issues with the crash on MethsofRelease and doing an uninstall, full clean and rebuild then deploy again resolved it.

Are you also able to put your changes into the sample project if its compiling and redeploying correctly? And I can use this to create a new ticket here on MAUI?

We use a few different custom configurations as we have different flavors of the app for different clients.

Finally we actually had this working on MethsofRelease and the problem just started at the time I was playing with compiled binding but I might try downgrade MAUI NuGet, maybe something else coincided with it.

[LeoJHarris]

@simonrozsival so having played with this further and on removing removing these property group items:

EnableLLVM, AndroidCreatePackagePerAbi, AndroidEnableMarshalMethods

Images are displaying now, not exactly sure which one i impacting things but seems to have resolved it for my release build.

[LeoJHarris]

In any event @simonrozsival thanks for looking into this for me! 👍 I may create a ticket from this when I have some time.

[simonrozsival]

I'm glad you were able to resolve the problem. All these build properties are specific to Android, so it would be best to open an issue in the dotnet/android repo.