I work for a small Point of Sale Company, and we are working on a in-house tool to make our lives easier when it comes to ticketing and troubleshooting. Part of my task in this tool is to write a 'softphone' in C# WPF that we can use to accept incoming and make ongoing calls with.
We currently use OnSIP as our SIP provider, and are looking to build custom software to essentially allow us to auto-generate support tickets based on the phone number of the incoming call. In addition we will need call transferring, recording, hold/wait, etc.
The question that seems to be causing me the most trouble is really where to begin on something like this. Thoughts?
I'm presuming this is a desktop application?
Lookup pjsip.org, it's a portable C library which is very well proven. It will allow you to do all that you are asking, although it'll take you some time to write the wrapper code - you can find examples on the internet, however we have written a wrapper ourselves which I'll check on as we had intended open sourcing it. This is because when we did this last year, the examples just didn't work too well :-)