Troubleshooting C# IntelliSense in VS Code

C# IntelliSense in VS Code kept stopping unexpectedly. In December 2022, I ran into another failure:

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System.Composition.Hosting.CompositionFailedException: No export was found for the contract 'ILoggerFactory'

OmniSharp had updated automatically. In settings.json, I changed omnisharp.path from latest to a pinned version:

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"omnisharp.path": "1.39.2",

Versions that worked together in this setup#

Automatic extension updates were a recurring source of problems in this project. This is the historical combination I found stable:

.NET Framework 4.7.1.
Unity’s VS Code package 1.2.0: set "com.unity.ide.vscode": "1.2.0" in manifest.json.
VS Code’s C# extension 1.24.0: use the arrow beside the uninstall button and choose Install Another Version.
OmniSharp 1.39.2: pin it with omnisharp.path in settings.json.

C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.1