Hi
My name is Mike, I am MCPD and Onvif expert.
I have completed various projects related to Onvif client and Onvif server software using .Net C#.
I have already done the task you are asking for, and have a WPF user control + Onvif code for establishing connection with Onvif Camera and displaying live video feed.
I can provide you a demo app which uses my components for your testing, and source code