In other blogs I have mentioned that DirectMath (where XNAMath has moved to) can only be accessed by C++.  Sooooo, just how do you use this in your C# code, etc.  Well you would create a Windows Runtime (WinRT) component.

A simple walkthrough can be found at: http://msdn.microsoft.com/en-us/library/windows/apps/hh441569(v=vs.110).aspx (which is a good tutorial)

Then you can use the directmath stuff in a MetroStyle app. image