I have to do some research on softphones for my PhD studies and I want to build one on my own to really get to know them.
http://voip-sip-sdk.com/p_266-how-to-build-a-softphone-voip.html seems to grant a very good but brief intro on the topic. Is there anybody who can tell me if the VoIP-SIP SDK is worth to try? (I use C# language, so please do not offer me Java or other solutions for the problem.)