Attachable Property Warning (XAML Compiling Error)

[dnx231]

Hi,
i am getting a warning on every line in XAML Code with DataGrid Extension.

This screenshot is from your SampleProject. The Extension works with no problems, but with this Warning the XAML Hot Reload doesn't work and i am unable to change XAML Code while Debugging.

Any advice?

[tom-englert]

This is an issue with the XAML editor - raise an issue for Visual Studio.

[tom-englert]

Duplicate of #53

[dnx231]

Hi,
i am using several extensions in my Project (e.g. Gong.Wpf.DragDrop) with no errors about attachable properties and i can't find any Issue reports for this behaviour in Google, Reddit, Stackoverflow.

Are you sure?

[tom-englert]

I've been so used over the years to see false errors like this in the XAML-designer, that I had stopped wondering about them.

However here I actually found what confuses the designer - I had marked the getters of some attached properties as extension methods, so they are easier to use from code.

Since the code compiles and runs, and only shows an error when loading into the designer, IMO this is really a bug in the designer.

I have removed the extension method signatures for all attached property getters in 2.6.0-beta1, hoping this will not create too much breaking changes in projects that use it.

[dnx231]

Thanks for your quick response and the fix!

[tom-englert]

@dnx231, @fchtngr, @mdomas1: here is the issue I've created for VS about the XAML designer, maybe you can vote for it to give it more attention:
https://developercommunity.visualstudio.com/t/xaml-designer-shows-xdg0012-when-the-attached-prop/1410871

[tom-englert]

There's a fix available in Visual Studio 2022 version 17.0 Preview 1, so I will not continue to maintain the workaround provided in 2.6.0-beta1.