How to send a post request to a Gtk WebView?

Question

This is basically what I've got.

var webview = new WebKit.WebView();
content_area.Add(webview);
var request = new NetworkRequest("http://example.com/resources/1");
request.Data.Add("description", "a description");
webview.LoadRequest(request);

I'm assuming request.Data is where I put variables, but it seems to be going through as a GET request.