I recently added explicit support for asynchronous programming to Modern C++ for the Windows Runtime. It now supports both PPL tasks as well as the new await keyword proposed for the C++ programming language to implement stackless coroutines (known as resumable functions). You can find more information along with a short video demo here:
The Modern C++ Library provides a Standard C++ language projection for the Windows Runtime. But what about asynchronous programming? Isn’t that ubiquitous in the new Windows API? It sure is and Modern has you covered.
Kenny Kerr 
Hello.
I have been watching for your library since june 2014. How can I try it?
I’m still working on it. Hopefully later this year.