Hi,
This looks like a Visual Studio issue. Have you tried waiting until the IntelliSense information is updated? Maybe this will help the message not repeat, as usually the IntelliSense information is generated only once when the project without the cached IntelliSense information is opened. This can take several minutes for a large project. Any subsequent usage of the same project should not have this message come up as any IntelliSense updates should be small and done in the background.
You can try disabling IntelliSense, but there may be no good way to turn IntelliSense completely off. It is possible to turn certain features off, but this may not affect IntelliSense information caching that your issue seems to be about. Disabling IntelliSense will not affect building or debugging your projects, however text editor features such as code suggestion will not be available.