This happened to me recently when I was trying to resolve a different issue. The original issue was that my home page had randomly stopped working in my ASP.Net MVC application and I’m still unsure why this happened.

When I was looking at my original issue I looked at the launchSettings.json file in the projects properties. I changed the ApplicationUrl setting but this didn’t resolve my original issue so I reverted the value. This resulted in the error above. Frustratingly, restarting etc didn’t resolve this issue.

The solution that worked for me was to remove the .vs folder. I didn’t try it but I’ve since discovered that simply removing applicationhost.config from the .vs folder may be a preferable option. This makes some sense as the app pools are defined in there.

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This issue has happened to me repeatedly on Visual Studio 2019 and the package concerned has varied considerably, it appears to be related to when I uninstall extensions that it goes particularly bad. Sometimes when you open Visual Studio you get a number of these messages and the option to…

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Steve Ellwood

Senior Integrations Officer at Doncaster Council Any views expressed are entirely my own.