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I installed Unity 2020.3.1f1 and upgraded one of my Unity projects to this version from 2019.2.12f1. In the Unity Editor the upgraded project built and ran and everything seemed fine.

However, when the project was opened Visual Studio 2019 hundreds of errors were flagged - the majority being CS0518 errors with messages like "Predefined type 'System.String' is not defined or imported".

Editing the Project code in Visual Studio is now impossible!

How do fix this problem?

AndyDBell
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  • in general always before upgrading you should [Clean up](https://stackoverflow.com/questions/56267842/cleaning-up-and-migrating-existing-unity-project-into-new-one-or-another-pc/56267992#56267992) your project from any dynamically generated stuff ;) – derHugo Aug 31 '20 at 05:56
  • Good advice - Thank you. – AndyDBell Aug 31 '20 at 22:54

1 Answers1

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I was able to correct this problem as follows:

Close Visual Studio

In Unity Editor 2020.3.1f1 : Edit->Preferences->External Tools

Button under Generate .csproj files Regenerate Project Files

After running Regenerate Project Files I opened Visual Studio 2019 again and the floods of CS0518 errors were gone. The VS projects behaved normally.

AndyDBell
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