Server.MapPath does not return the right physical path mapped to a virtual directory in Web-App subfolder

I create a web site and mapped it to the

D:\MyWebApp

and in Plugins sub directory I create a virtual directory and mapped it to

D:\Project\Presentation\Web\Accounting

.
the problem is when I want to get the physical path of the phisical path of http://localhost/Plugins/Accounting I get wrong result.

both

Server.MapPath("~/Plugins/Accounting") and Server.MapPath("/Plugins/Accounting")

returns

'D:\MyWebApp\Plugins\Accounting'

that does not exist physically. I want to get

D:\Project\Presentation\Web\Accounting

.
I search for it and just get below lines:

Server.MapPath(".") returns the current physical directory of the file (e.g. aspx) being executed
Server.MapPath("..") returns the parent directory
Server.MapPath("~") returns the physical path to the root of the application
Server.MapPath("/") returns the physical path to the root of the domain name (is not necessarily the same as the root of the application)

but in my case (virtual directory in a subfolder), it's not work !!!
I use IIS8 and Asp.Net-Mvc 4 and C#4.
how can I do this?

Tags: C#, ASP, MVC, IIS