Async Web Request - Wait For Request

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C#

I am trying to implement Async on my application through the await and async methods in NET 4.5 however, I need the web request to finish for the collections to filled but I do not want my UI to freeze up as I would like to transition to a loading page during the request.

HTML Request > Collections > UI.

private Task<string> WebRequestAsync(String urlforcollection)
        {
            return Task.Factory.StartNew(() =>
            {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(urlforcollection);
                request.Proxy = null;
                request.Method = "GET";
                WebResponse response = request.GetResponse();
                Stream mystream = response.GetResponseStream();
                htmlDocument.Load(mystream);
                response.Close();
                MessageBox.Show("Finished");
                return "";
            });
}

await WebRequestAsync("http://fartjuice.org.uk");

if (WebRequestAsync("http://fartjuice.org.uk").IsCompleted == true)
{
AddDataToCollections();
LoadToUI();
}

For some reason this does not work, I don't get the message show and my program loads to the page that displays the information without adding the binded information?

How can I do this? Thank you!.