Hi @Lyubomir Radev,
Welcome to Microsoft Q&A!
If it is an Avalonia application, Avalonia XAML files have the extension .axaml not .xaml.
You need to install Avalonia for Visual Studio 2022 extension to get IntelliSense support for Avalonia XAML.
If you have installed the extension, please uninstall it and reinstall the latest version 11.5.
If the IntelliSense still doesn’t work in Avalonia application, I suppose it may be a known issue. You can see the similar issue.
You need to contact the Avalonia Team in GitHub to check it. Thanks for your understanding!
Sincerely,
Anna
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