Silverlight receive a response from a handler

Question

I have a Silverlight Application that sits on a web page. It allows a user to upload multiple documents to a server. When I begin uploading a document to the server I will make a call to a handler with a POST request and I send it in chunks if the file is too big with the following code:

private void UploadFileEx()
{
    Status = FileUploadStatus.Uploading;
    var temp = FileLength - BytesUploaded;

    var ub = new UriBuilder(_urlServer);
    var complete = temp <= ChunkSize;

    ub.Query = string.Format("{3}locationCode={4}&filename={0}&StartByte={1}&Complete={2}", RockDocumentName, BytesUploaded, complete,
                                string.IsNullOrEmpty(ub.Query) ? string.Empty : string.Format("{0}&", ub.Query.Remove(0, 1)), _locationCode);

    var webrequest = (HttpWebRequest) WebRequest.Create(ub.Uri);
    webrequest.Method = "POST";

    // Begins an asynchronous request for a Stream object to use to write data.
    // The asynchronous callback method uses the EndGetRequestStream method to return the actual stream.
    // This means
    webrequest.BeginGetRequestStream(WriteCallback, webrequest);
}

private void WriteCallback(IAsyncResult asynchronousResult)
{
    var webrequest = (HttpWebRequest) asynchronousResult.AsyncState;
    // End the operation.
    // Here we obtain the stream to write the request
    var requestStream = webrequest.EndGetRequestStream(asynchronousResult);

    var buffer = new Byte[4096];
    int bytesRead;
    var tempTotal = 0;

    Stream fileStream = File.OpenRead();

    fileStream.Position = BytesUploaded;
    while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0 && tempTotal + bytesRead < ChunkSize)
    {
        requestStream.Write(buffer, 0, bytesRead);
        requestStream.Flush();
        BytesUploaded += bytesRead;
        tempTotal += bytesRead;

        if (UploadProgressChanged != null)
        {
            var percent = (int) ((BytesUploaded/(double) FileLength)*100);
            var args = new UploadProgressChangedEventArgs(percent, bytesRead, BytesUploaded, FileLength,
                                                            RockDocumentName);
            Dispatcher.BeginInvoke(() => UploadProgressChanged(this, args));
        }
    }

    fileStream.Close();
    requestStream.Close();

    // Whenever the operation is ready call the ReadCallback method (when this method
    // is called we know that the chunk of file has arrived successfully to the server,
    // it's time to process the next chunk).
    webrequest.BeginGetResponse(ReadCallback, webrequest);
}

I would like my handler to return back my documents name (I generate a new file name for each document in the handler because we have a document naming standard that's being used). So i coded my AsyncCallback like this which I was expecting the AsyncState would return the header I thought I was settting in the handler:

private void ReadCallback(IAsyncResult asynchronousResult)
{
    var documentName = ((System.Net.BrowserHttpWebRequest)asynchronousResult.AsyncState).Headers["documentname"].ToString();

    if (BytesUploaded < FileLength)
        UploadFileEx();
    else
    {
        Status = FileUploadStatus.Complete;
    }
}

Here is my Handler:

public void ProcessRequest(HttpContext context) {
      Context = context;
      UploadFile();
      //context.Request.Headers.Add("documentname", "testfilename.pdf");
      context.Response.Headers.Add("documentname", "testfilename.pdf"); 
}

This isn't working as I had thought. What am I doing wrong? Am I setting the header wrong in my handler? Is there another way for my handler to speak to the Silverlight client app?

Any help would be appreciated. Thanks in advance!

Answer 1

You may have more luck if your handler sends back the document name as part of the Response body rather than as a Header.

Try this code and see what you get:

private void ReadCallback(IAsyncResult asynchronousResult)
{
    var webRequest = (HttpWebRequest) asynchronousResult.AsyncState;
    var webResponse = (HttpWebResponse) webRequest.EndGetResponse(asynchronousResult);
    var reader = new StreamReader(webResponse.GetResponseStream());
    var documentName = reader.ReadToEnd();
    reader.Close();


    if (BytesUploaded < FileLength)
        UploadFileEx();
    else
    {
        DocumentName = documentName;
        Status = FileUploadStatus.Complete;
    }
}

And in ProcessRequest:

Context.Response.Write(“Document Name”);