`UIElementExtensions.Elevation` breaks VS designer

[artemious7]

Current behavior

When setting UIElementExtensions.Elevation attached property for an element, the Visual Studio designer shows an error, but it compiles fine and works fine in a running app.

Expected behavior

The VS designer must show the rendered XAML.

How to reproduce it (as minimally and precisely as possible)

App4.zip

Set Elevation, build the UWP project, see the error in the VS designer.

Workaround

Set UIElementExtensions.Elevation via code-behind or don't use it at all.

Environment

Nuget Package:

• [x] Uno.UI
• [ ] Uno.WinUI / Uno.WinUI.WebAssembly / Uno.WinUI.Skia
• [ ] Uno.SourceGenerationTasks
• [ ] Uno.UI.RemoteControl / Uno.WinUI.RemoteControl
• [ ] Other:

Nuget Package Version(s):

Affected platform(s):

• [ ] iOS
• [ ] Android
• [ ] WebAssembly
• [ ] WebAssembly renderers for Xamarin.Forms
• [ ] macOS
• [ ] Skia
  • [ ] WPF
  • [ ] GTK (Linux)
  • [ ] Tizen
• [ ] Windows
• [ ] Build tasks
• [ ] Solution Templates

IDE:

• [ ] Visual Studio 2017 (version: )
• [x] Visual Studio 2019 (version: 16.9.2), Version 16.10.0 Preview 1.0
• [ ] Visual Studio for Mac (version: )
• [ ] Rider Windows (version: )
• [ ] Rider macOS (version: )
• [ ] Visual Studio Code (version: )

Relevant plugins:

• [ ] Resharper (version: )

Anything else we need to know?

To fix this, just remove this in this UIElement element. VS doesn't like these are extension methods.

https://github.com/unoplatform/uno/blob/a6bb7ecaceb1908172a896733c74871ca261a799/src/Uno.UI.Toolkit/UIElementExtensions.cs#L30

https://github.com/unoplatform/uno/blob/a6bb7ecaceb1908172a896733c74871ca261a799/src/Uno.UI.Toolkit/UIElementExtensions.cs#L35

[Youssef1313]

Instead of introducing a breaking change, why this is not considered a bug in VS designer?

[Youssef1313]

The designer isn't working at all for me in a plain new UWP project:

Also it looks like WinUI doesn't even support a designer yet? https://github.com/microsoft/microsoft-ui-xaml/issues/5917

It's worth noting that the code doesn't give IntelliSense warnings:

In the issue, it used to have a squiggly warning, so something might have already been fixed in Visual Studio.

[MartinZikmund]

So maybe this can be closed now? The designer is not even planned for WinUI so far...

[jeromelaban]

Yes, let's close for now.