interestingly it works when you put all the parameters in the call to Create the instance of HttpWebRequest like this:
and skips the lineCode:HttpWebRequest httpWebRequest =
(HttpWebRequest)WebRequest.Create("http://friendfeed-api.com/v2/entry?body=Hello API&format=xml");
"Hallo API" was successfuly added to my feedCode:Stream dataStream = httpWebRequest.GetRequestStream();