/// <summary>
/// Asynchronously downloads an xml file from the specified url
/// </summary>
/// <param name="url"></param>
/// <param name="callback">A <see cref="DownloadXmlCompletedCallback"/> to be invoked when the request is completed</param>
/// <param name="userState">A state object to be returned to the callback</param>
/// <returns></returns>
public object DownloadXmlAsync(string url, HttpPostData postData, DownloadXmlCompletedCallback callback, object userState)
{
string urlValidationError;
if (!IsValidURL(url, out urlValidationError))
{
throw new ArgumentException(urlValidationError);
}
XmlRequestAsyncState state = new XmlRequestAsyncState(callback, DownloadXmlAsyncCompleted, userState);
HttpWebServiceRequest request = GetRequest();
request.GetResponseAsync(url, new MemoryStream(), XML_ACCEPT, postData, state);
return request;
}
