Thank you for contacting us.
This behavior is not expected. The Visual Studio extensions are designed to be as lightweight as possible. They do not consume system resources when they are not being used. In addition, the extensions do not interfere in the build process of the studio.
I would suggest to reinstall the UI for ASP.NET MVC extensions and check if the issue still exists.
Another thing you can do is to install another extensions to check if the CPU consumption is still high.
Please do not hesitate to contact us in case further questions arise.
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