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 ignore the message in future doesn’t prevent it from recurring.

The solution to this is remarkably straightforward, firstly shutdown all instances of Visual Studio, then delete the ComponentModelCache folder which can be found in the following folder

C:\Users\<UserName>\AppData\Local\Microsoft\VisualStudio\16.xxx

the user name is your login name. You may find in the VisualStudio folder a number of folders that are 16.xxx — I just deleted the ComponentModelCache folder from the one that had been used most recently and all seemed fine.

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Steve Ellwood

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