// Header field definitions // http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html httpRequest.Open("GET", txtUrl.Text, true, "", ""); httpRequest.SetRequestHeader("Accept", "text/html"); // Cache-Control header - "no-cache" - Do not cache the http response httpRequest.SetRequestHeader("Cache-Control", "no-cache"); httpRequest.Send(msg); ///// httpRequest.Open // lgRequest is a HttpWebRequest object lgRequest = (HttpWebRequest)WebRequest.CreateDefault(uriObj); lgRequest.Method = Method; // "GET" ///// httpRequest.SetRequestHeader (just sets my request header attributes of the HttpWebRequest object) lgRequest.Accept = headerValue; // "text/html" ///// httpRequest.Send if (lgReadyState != clientState.LOADING) throw new InvalidOperationException("Sending a message is not allowed at this ReadyState"); // Assign callback method, this line gives me the exception when using "GET" IAsyncResult res = lgRequest.BeginGetRequestStream(new AsyncCallback(ReqCallback),lgRequest); lgReadyState = clientState.LOADED; ///// httpRequest.ReqCallBack HttpWebRequest req = (HttpWebRequest)ar.AsyncState; // Code below used to write in POST data to connection header, using GET so commented out //Stream stream = req.EndGetRequestStream(ar); //StreamWriter streamW = new StreamWriter(stream); //streamW.Write(lgMsg); //streamW.Close(); //stream.Close(); IAsyncResult resp = req.BeginGetResponse(new AsyncCallback(RespCallback), req);