How to get around the threading limit

We created a chess game in which the actual engine is running on a separate thread. Everything works fine building the project for desktop, however building it for Windows Store results in the System.Threading namespace not being recognized. So I can build for a Windows 8(.1) desktop but can't sell it on the Windows Store ... hmmm.
Anyone any idea on how to get around this limitation? Do I miss something?
I already tried to change the engine to a coroutine approach but needless to say this is way too expensive as Unity and the chess engine are on the same thread.

Edit: Error message when building for Windows Store: Assets\Scripts\Engine\ChessEngine.cs(325,13): error CS0103: The name 'ThreadPool' does not exist in the current context

 

I'm completely lost converting the project to Windows Store

I'm using the following code (snippets):

Code (CSharp):

1. #if NETFX_CORE
2.   using Windows.System.Threading;
3. #else
4.   using System.Threading;
5. #endif

at the start of the script and following code:

Code (CSharp):

1. #if !NETFX_CORE
2.   myThinker = new Thread(new ThreadStart(Thinker));
3.   myThinker.Start();
4. #else
5.   IAsyncAction asyncAction = Windows.System.Threading.ThreadPool.RunASync((workItem) =>
6.   {
7.   Thinker();
8.   });
9.   m_workItem = asyncAction;
10. #endif

but apparently I'm missing something but I can't pinpoint what exactly.

However building the project results into the following errors:
Assets\Scripts\Engine\ChessEngine.cs(328,13): error CS0246: The type or namespace name 'IAsyncAction' could not be found (are you missing a using directive or an assembly reference?)
Assets\Scripts\Engine\ChessEngine.cs(328,76): error CS0117: 'Windows.System.Threading.ThreadPool' does not contain a definition for 'RunASync'

I'm trying to follow the example Microsoft provides at http://msdn.microsoft.com/en-us/library/windows/apps/jj248677.aspx

 

Thanks for pointing that out to me, I'm loving the CamelCase .
Just downloaded the complete example repo http://code.msdn.microsoft.com/windowsapps/Windows-8-Modern-Style-App-Samples, looks like a great starting point for those taking there first steps into Windows Store development.