This article will have more information about logical versus virtual file paths in Asp.Net:
MapPath - DotNetPerls[
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UPDATE: Due to the title of the question being changed, the above response is now incorrect. Below is a revised response:
Web applications work under a reduced set of permissions to stop security breaches of the hosting service above the level of the web application itself. So
disable root folder in windows using ASP.NET C# would not be possible as this is the responsibility of the hosting service, IIS in this case.