C# HttpWebRequest Form Post with Progress Tracking (for uploading potentially large files)

Question

I've got a winforms application I'm writing that posts files to a web application (not mine). I've got things working just fine as far as posting the files themselves go, my issue is that I'd like to provide some indication of how far along I am with the sending the request.

The code below is my attempt to use BeginGetResponse to that end - and this is where I discovered that the Request still blocks.

Any suggestions on where I can begin to look?

    public void Dummy()
    {
        Dictionary<string, string> fields = new Dictionary<string, string>();
        fields.Add("key", "something");

        HttpWebRequest hr = WebRequest.Create("http://somesite.com/api/something.xml") as HttpWebRequest;
        string bound = "----------------------------" + DateTime.Now.Ticks.ToString("x");
        hr.ContentType = "multipart/form-data; boundary=" + bound;
        hr.Method = "POST";
        hr.KeepAlive = true;
        hr.Credentials = CredentialCache.DefaultCredentials;

        byte[] boundBytes = Encoding.ASCII.GetBytes("\r\n--" + bound + "\r\n");
        string formDataTemplate = "\r\n--" + bound + "\r\nContent-Disposition: form-data; name=\"{0}\";\r\n\r\n{1}";

        Stream s = hr.GetRequestStream();

        foreach (string key in fields.Keys)
        {
            byte[] formItemBytes = Encoding.UTF8.GetBytes(
                string.Format(formDataTemplate, key, fields[key]));
            s.Write(formItemBytes, 0, formItemBytes.Length);
        }

        s.Write(boundBytes, 0, boundBytes.Length);

        string headerTemplate = 
            "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\n Content-Type: application/octet-stream\r\n\r\n";

        List<string> files = new List<string> { Server.MapPath("/Images/Phillip.jpg") };

        foreach (string f in files)
        {
            byte[] headerBytes = Encoding.UTF8.GetBytes(
                String.Format(headerTemplate, "image", f));

            s.Write(headerBytes, 0, headerBytes.Length);
            FileStream fs = new FileStream(f, FileMode.Open, FileAccess.Read);
            int bytesRead = 0;
            byte[] buffer = new byte[1024];
            while ((bytesRead = fs.Read(buffer, 0, buffer.Length)) != 0)
            {
                s.Write(buffer, 0, buffer.Length);
            }

            s.Write(boundBytes, 0, boundBytes.Length);
            fs.Close();
        }

        s.Close();

        string respString ="";
        hr.BeginGetResponse((IAsyncResult res) =>
            {
                WebResponse resp = ((HttpWebRequest)res.AsyncState).EndGetResponse(res);

                StreamReader respReader = new StreamReader(resp.GetResponseStream());
                respString = respReader.ReadToEnd();
                resp.Close();
                resp = null;
            }, hr);

        while (!hr.HaveResponse)
        {
            Debug.Write("hiya bob!");
            Thread.Sleep(150);
        }

        Debug.Write(respString);
        hr = null;
    }

Answer 1

Ok, figured it out. The HttpWebRequest object, if you set the ContentLength property, will directly connect it's ResponseStream to the network socket when you call GetRequestStream(). This then allows you to track your progress by writing directly to this stream.

Pseudo Code:

Request r = CreateWebRequest(Url)
r.ContentLength = CalculateRequestLength(fields, files)
Stream requestStream = r.GetRequestStream()
while(moreData)
{
  requestStream.write(someData);
  UpdateProgress();
}
r.GetResponse();

Working Code:

   public void Dummy()
    {
        Dictionary<string, string> fields = new Dictionary<string, string>();
        fields.Add("key", "something");

        HttpWebRequest hr = WebRequest.Create("http://imgur.com/api/upload.xml") as HttpWebRequest;
        string bound = "----------------------------" + DateTime.Now.Ticks.ToString("x");
        hr.ContentType = "multipart/form-data; boundary=" + bound;
        hr.Method = "POST";
        hr.KeepAlive = true;
        hr.Credentials = CredentialCache.DefaultCredentials;

        byte[] boundBytes = Encoding.ASCII.GetBytes("\r\n--" + bound + "\r\n");
        string formDataTemplate = "\r\n--" + bound + "\r\nContent-Disposition: form-data; name=\"{0}\";\r\n\r\n{1}";

        //add fields + a boundary
        MemoryStream fieldData = new MemoryStream();
        foreach (string key in fields.Keys)
        {
            byte[] formItemBytes = Encoding.UTF8.GetBytes(
                string.Format(formDataTemplate, key, fields[key]));
            fieldData.Write(formItemBytes, 0, formItemBytes.Length);
        }
        fieldData.Write(boundBytes, 0, boundBytes.Length);

        //calculate the total length we expect to send
        List<string> files = new List<string> { Server.MapPath("/Images/Phillip.jpg") };
        string headerTemplate =
            "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\n Content-Type: application/octet-stream\r\n\r\n";
        long fileBytes = 0;
        foreach (string f in files)
        {
            byte[] headerBytes = Encoding.UTF8.GetBytes(
                String.Format(headerTemplate, "image", f));
            FileStream fs = new FileStream(f, FileMode.Open, FileAccess.Read);

            fileBytes += headerBytes.Length;
            fileBytes += fs.Length;
            fileBytes += boundBytes.Length;
            fs.Close();
        }

        hr.ContentLength = fieldData.Length + fileBytes;

        Stream s = hr.GetRequestStream();           
        //write the fields to the request stream
        Debug.WriteLine("sending field data");
        fieldData.WriteTo(s);

        //write the files to the request stream
        Debug.WriteLine("sending file data");
        foreach (string f in files)
        {
            byte[] headerBytes = Encoding.UTF8.GetBytes(
                String.Format(headerTemplate, "image", f));
            s.Write(headerBytes, 0, headerBytes.Length);

            FileStream fs = new FileStream(f, FileMode.Open, FileAccess.Read);
            int bytesRead = 0;
            long bytesSoFar = 0;
            byte[] buffer = new byte[10240];
            while ((bytesRead = fs.Read(buffer, 0, buffer.Length)) != 0)
            {
                bytesSoFar += bytesRead;
                s.Write(buffer, 0, bytesRead);
                Debug.WriteLine(String.Format("sending file data {0:0.000}%", (bytesSoFar * 100.0f) / fs.Length));
            }

            s.Write(boundBytes, 0, boundBytes.Length);
            fs.Close();
        }

        s.Close();

        GetResponseDel d = new GetResponseDel(GetResponse);
        ResponseData data = new ResponseData { del = d };
        d.BeginInvoke(hr, EndGetResponse, data);

        while (!hr.HaveResponse)
        {
            Debug.Write("waiting for response" + "\n");
            Thread.Sleep(150);
        }

        Debug.Write(data.responseString);
        hr = null;
    }

    delegate WebResponse GetResponseDel(HttpWebRequest hr);
    private WebResponse GetResponse(HttpWebRequest hr)
    {
        return hr.GetResponse();
    }

    class ResponseData
    {
        public GetResponseDel del { get; set; }
        public string responseString { get; set; }
    }

    private void EndGetResponse(IAsyncResult res)
    {
        ResponseData data = (ResponseData)res.AsyncState;
        GetResponseDel d = data.del;

        WebResponse r = d.EndInvoke(res);
        data.responseString = new StreamReader(r.GetResponseStream()).ReadToEnd();
    }