how to get button click response on webpage in c# wp8.1?

I'm trying to get data from a webpage using HttpClient but my desired data is shown in page after a button click. how i can click that button programmatically and then get the response.

this is what i tried

        HttpClient client = new HttpClient();
        var doc = new HtmlAgilityPack.HtmlDocument();
        string uritolaunch = "webpageaddress";
        var uri = new Uri(uritolaunch);
        var html = await client.GetStringAsync(uri);
        doc.LoadHtml(html);

this is what i got from Firefox inspector:

<a data-observed="1" data-trigger="abc">abc</a>

this is its event

 ``responder = function(event) {Event.extend(event, element);handler.call(element, event);}