Maybe my post is not at the right place, if no please put it where it is required.

I have lately started learning C and C++. I decided to build an own application and while I was browsing on the Internet found an interesting site. On the site there can be several sample programs found which are based upon an SDK called Ozeki VoIP SIP SDK. Have you used it before? My problem is that I find the samples are good but they are in C#. Since I have no experience in C# could you tell me a way how to start using this software? Or in your opinion I should practice in C or C++ and study C# first?