Getting Project Root Path In Controller ASP.NET MVC?

I am using dotlesscss for my css and I remember how to use 开发者_如何学Gothat but what I am forgetting is how to get the root project path so that I can generate the full file path to my .less file to get for the less engine to parse. How do I get the project root path so that I can generate the path for my less files?

Server.MapPath("~");

or:

HostingEnvironment.ApplicationPhysicalPath