How to build a softphone in C#?

Question

Hi all!

I am a beginner developer and now I am planning to develop softphone in C# language. After a little research I have found this site:  http://www.voip-sip-sdk.com/p_266-how-to-build-a-softphone-using-sip-and-voip-voip.html 
I have some questions about it: Would you recommend it to me? Has anybody tried it yet? And if yes could you give me a little review of it?

Thanks for your help!

Cheers!