How to call an async method in a c++ DLL function from a test application

  asynchronous, c++, c++-winrt, multithreading

I am doing a c++/winrt DLL project for a low energy Bluetooth device communication. Almost all the Bluetooth functions are asynchronous. I have a testing c++ console application which will call each of the DLL functions.
My doubt is, how can I hold the test application main thread until the completion of the async DLL function execution.
After checking the completion I need to call the other method.
Please suggest some better ideas.

Source: Windows Questions C++