How to build a softphone (using SIP protocol) using C#

Question

I have this challenge to build an sip softphone using c# or .net technologies.

Please guide me the technology, requirements and specifications that is needed to build

Answer 1

Konnetic provide fully managed SIP components for .NET development.

Their SIP .NET SDK is available here and is probably the most comprehensive. They also provide an MSRP library.

Otherwise, Microsoft's Lync server comes with a very good managed SIP library, available here: www.microsoft.com/en-us/lync/default.aspx