When opening a web project:

The project you are trying to open is a Web project. You need to open it by specifying its URL path.

Create a file called c:\inetpub\wwwroot\Folder\MyProject.csproj.webinfo and add:

<VisualStudioUNCWeb>
    <Web URLPath = "http://localhost/Folder/MyProject.csproj" />
</VisualStudioUNCWeb>

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