Httpwebrequest asynchronous thread synchronization in Windows Phone

public class RequestState
    {
        public HttpWebRequest request {get; set;}
        public HttpWebResponse response {get; set;}
        public Stream streamResponse {get; set;}
    }

    public class HttpHelper
    {
        public delegate void GetData (string text);

        public event GetData Data;

        public class HttpCallBackEvent
        {
            public HttpWebRequest request;
            public byte [] file;
            public string name;
            public string fileName;

        }


        public static ManualResetEvent allDone = new ManualResetEvent (false);

        public Stream HttpGet (string url)
        {
            HttpWebRequest request = (HttpWebRequest) WebRequest.Create (new Uri (url));
            request.Method = "GET";

            RequestState state = new RequestState ();
            state.request = request;

            request.BeginGetResponse (webResponseCallack, state);
            allDone.Reset ();
            allDone.WaitOne ();

            return state.streamResponse;
        }

        private void webResponseCallack (IAsyncResult result)
        {
            try
            {
                RequestState state = (RequestState) result.AsyncState;
                HttpWebRequest request = state.request;
                state.response = (HttpWebResponse) request.EndGetResponse (result);
                state.streamResponse = state.response.GetResponseStream ();
                
            }
            catch
            {}
            finally
            {
                allDone.Set ();
            }
        } 

}