Both should work together. There are, however, some caveats. In particular, as per https://code.visualstudio.com/docs/csharp/cs-dev-kit-faq
Whole line completions are disabled when the GitHub Copilot extension is enabled to allow you to take advantage of the more advanced AI completion capabilities. You can verify that Copilot is enabled by checking if the Copilot logo is present in the lower right corner of VS Code
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Marcin