False-positive errors in XAML preview when Windows is not selected as target

[sigmarsson]

Current behavior

1. Created a page for tab navigation.
2. Set Page Background as Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
3. Encountering a compilation error on Wasm as

Expected behavior

It ought to work like on Windows Desktop.

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

No response

Workaround

No response

Works on UWP/WinUI

Yes

Environment

Uno.WinUI / Uno.WinUI.WebAssembly / Uno.WinUI.Skia, Uno.UI.RemoteControl / Uno.WinUI.RemoteControl

NuGet package version(s)

    <ItemGroup>
      <PackageReference Include="DryIoc.dll" Version="4.8.8" />
      <PackageReference Include="LiveChartsCore.SkiaSharpView.Uno" Version="2.0.0-beta.220" />
      <PackageReference Include="Microsoft.Extensions.Logging" Version="6.0.0" />
      <PackageReference Include="Microsoft.Windows.Compatibility" Version="6.0.0" />
      <PackageReference Include="Uno.Extensions.Logging.WebAssembly.Console" Version="1.3.0" />
      <PackageReference Include="Uno.WinUI.WebAssembly" Version="4.2.6" />
      <PackageReference Include="Uno.WinUI.RemoteControl" Version="4.2.6" Condition="'$(Configuration)'=='Debug'" />
      <PackageReference Include="Uno.Wasm.Bootstrap" Version="3.3.1" />
      <PackageReference Include="Uno.Wasm.Bootstrap.DevServer" Version="3.3.1" />
    </ItemGroup>

Affected platforms

WebAssembly

IDE

No response

IDE version

Version 17.2.0

Relevant plugins

No response

Anything else we need to know?

No response

[jeromelaban]

Note that the repro cannot work, since LiveChartsCore.SkiaSharpView.Uno references Uno.UI, not Uno.WinUI. LiveCharts can't yet be updated until mono/SkiaSharp#1787 is fixed.

Make sure to validate with Uno.UI first.

[fsol11]

This happens for me as well. The project compiles. It is an Intellisense error only. Looks like there are some issues in Uno libraries that make Intellisense not work correctly. Lots of this type of errors happen.

[jeromelaban]

@lotrasoft that's correct, it's a Visual Studio issue that we've working with Microsoft to improve. If you select the Windows project in the top left selector in the XAML editor, this error should go away.

[fsol11]

Thanks, but there is no selector on XAML editor:

[jeromelaban]

This is curious. Where is the file located in your solution? In which project, specifically?

[fsol11]

@jeromelaban The Xaml file is located in the Shared project. And note that the WYSIWYG editor for XAML is also not available.

[jeromelaban]

It is expected that the designer is not available microsoft/microsoft-ui-xaml#5917, but the curious part is the missing top level bar. Can you try closing all the editor files, then close visual studio, then reopen the solution?

[fsol11]

I have done that 10000 times. Does not help. Note that with Uno, a few internal components of Visual Studio crash. Here is an example (look at the brown bars):

[jeromelaban]

Thanks for the update. Two things:

• Can you try unloading all projects except the shared project and the windows project and see if it helps?
• Can you attach here the two "Show stack trace" in blue that VS is showing at the top?

[fsol11]

I just installed Visual Studio update 17.4.4, and looks like the problem has been solved. The XAML toolbar now shows up and the ThemeResource error is gone.

[muhammetozeski]

I have same error.

Mostly same with lotrasoft but my vs is that "Microsoft Visual Studio Community 2022 (64-bit) - Preview
Version 17.5.0 Preview 3.0"
Using libraries are like this:

[jeromelaban]

@muhammet484 make sure to select the .Windows project in the top left selector.

[muhammetozeski]

@muhammet484 make sure to select the .Windows project in the top left selector.

do you mean this? I selected the windows already

you can also check my screen:

[jeromelaban]

@muhammet484 this selector, specifically:

[muhammetozeski]

thanks it solved the problem.

[dallyh]

@muhammet484 this selector, specifically:

I would like to address this issue a little more. Let's say I'd like to build apps only for mobile platforms (Android/iOS) because I'm not interested in developing an app for other platforms. When I generate a new project from template using custom settings (just Android and iOS or just one of them as platforms), then this workaround doesn't work, because i cannot select "Windows" nor "UWP" from the projects dropdown. Is there anything known I can do with this? Every issue I've found pointed me to selecting "Windows" from the dropdown menu, which works if I generate a project also targetting that platform.

[MartinZikmund]

@dallyh This is unfortunately true, we are using built-in XAML intellisense provided by Microsoft, which is only compatible with the Windows target. this causes the underlines in other cases. We were able to avoid these problems by implementing a custom IntelliSense provider in Visual Studio Code, but on VS 2022 this is a much more complex task. For now the recommendation is to include the Windows project there even if it is not going to be used as a production environment - it is useful for IntelliSense and even debugging.

[MartinZikmund]

It would be useful if we could automatically detect that non-Windows target is selected when a .xaml file is opened and switch it for the user, but it does not resolve the situation when the Windows target is not selected in the Wizard