>Don't know if it could be the problem but you could check that the website itself is targeting .NET 4 (Properties/ASP.NET: ASP.NET version

The application pool is v4.0.

Under the site itself, I cannot find a related setting for that. Note that this is a virtual directory on my PC. So, it goes like http://localhost/LevelExtreme20. Is there an ASP.NET setting at the Web site level itself, so to check what you are making reference to, on a virtual directory?