See my blo article here: http://www.hjgode.de/wp/2009/06/14/mdiwatch2/
It shows how to use POST to send data to a server (java servlet). The code uses HttpWebRequest and then builds the POST stream.
In a simpler form you just need to use HttpWebRequest and the just build your special URI: http://msdn.microsoft.com/en-us/library/debx8sh9.aspx