void OnDownloadStringCompleted(object aSender, DownloadStringCompletedEventArgs aArgs)
{
QueryNextSite();
var handler = (Action<REST, RESTResult>)aArgs.UserState;
var result = new RESTResult(aArgs);
if (result.Error == null && !result.Cancelled && !string.IsNullOrEmpty(aArgs.Result))
ParseData(XDocument.Parse(aArgs.Result, LoadOptions.None));
handler(this, result);
}