How to detect external IP, with simple c# code (kind of like www.whatismyip.com)

Question

What ever needs to be done, I gave up on my static IP because it was too expansive, but I can still do webhost, if my computer checks my ip every  2 minutes, and if different, update some file, and automate changes to php, html files, etc.

I just need to detect my External IP with c#, not local ip like 192.168.1.1.

Thanks!!!!