Question

I have the following class (I take it from an example on the net, the only thing I’ve modified is that I use an IP address and port instead of a domain name):

public class ConnectionManager
{
    private static ManualResetEvent allDone = new ManualResetEvent(false);
    private string message = "foobar";

    public Action MessageSent;
    public Action<string> MessageReceived;
    public void SendMessage()
    {
          // Create a new HttpWebRequest object.
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://10.1.91.48:3330/");

        request.ContentType = "application/json; charset=utf-8";
        request.Accept = "application/json";
        // Set the Method property to 'POST' to post data to the URI.
        request.Method = "POST";

        // start the asynchronous operation
        request.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), request);
        MessageSent();
        // Keep the main thread from continuing while the asynchronous 
        // operation completes. A real world application 
        // could do something useful such as updating its user interface. 
        allDone.WaitOne();
    }
    private void GetRequestStreamCallback(IAsyncResult asynchronousResult)
    {
        HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;

        // End the operation
        Stream postStream = request.EndGetRequestStream(asynchronousResult);


        // Convert the string into a byte array. 
        byte[] byteArray = Encoding.UTF8.GetBytes(message);

        // Write to the request stream.
        postStream.Write(byteArray, 0, byteArray.Length);
        postStream.Close();

        // Start the asynchronous operation to get the response
        request.BeginGetResponse(new AsyncCallback(GetResponseCallback), request);
    }

    private void GetResponseCallback(IAsyncResult asynchronousResult)
    {
        HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;

        // End the operation
        HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asynchronousResult);
        Stream streamResponse = response.GetResponseStream();
        StreamReader streamRead = new StreamReader(streamResponse);
        string responseString = streamRead.ReadToEnd();
        Console.WriteLine(responseString);
        // Close the stream object
        streamResponse.Close();
        streamRead.Close();

        // Release the HttpWebResponse
        response.Close();
        allDone.Set();

        MessageReceived(responseString);
    }
}

The code above fails to send the message. If I step, when I’m inside GetRequestStreamCallback I can see inside IAsyncResult the following error:

AsyncWaitHandle = ‘asynchronousResult.AsyncWaitHandle’ threw an
exception of type ‘System.NotSupportedException’

What am I doing wrong? How can I fix this code?

Answer 1

I ended up using WebClient:

WebClient wc = new WebClient();
wc.DownloadStringCompleted += ReadServerResponse;
wc.DownloadStringAsync(new Uri(url));