CODEWITHSUNDEEP
c#multithreadingsilverlightevents
as-cii
as-cii

Reputation: 13019

Silverlight 4 Threading Problems

recently I've been developing an application in Silverlight that uses uploading.
I use WebClient class to communicate with an HttpHandler that is in my server. The methods provided by WebClient are asynchronous and use Event-based APM: having in mind that the scope of Silverlight is to have a fluid UI that doesn't blocks I wanted, for fun, to try making the calls synchronous.

Code

AutoResetEvent _uploadedEvent = new AutoResetEvent(false);

foreach (var item in _fileInfos)
        {
            WebClient client = new WebClient();

            client.OpenWriteCompleted += (sender, e) =>
            {
                try
                {
                    using (FileStream fs = item.OpenRead())
                    using (Stream stream = y.Result)
                    {
                        while (true)
                        {
                            byte[] buffer = new byte[8192];

                            int readBytes = fs.Read(buffer, 0, buffer.Length);
                            if (readBytes == 0)
                                break;

                            stream.Write(buffer, 0, readBytes);
                        }
                    }
                }
                finally
                {
                    _uploadedEvent.Set();
                }
            };

            client.OpenWriteAsync(new Uri(_receiverUri));

            _uploadedEvent.WaitOne();
        }

The Problem

This way to make the calls synchronous doesn't work in Silverlight but it does in WPF. Right now I'm noticing I'm not the only one to have this problem: https://stackoverflow.com/questions/3819650/silverlight-httprequest-thread-problem

Where do you think is the problem?

Thanks in advance.
AS-CII.

Upvotes: 1

Views: 794

Answers (1)

Brian
Brian

Reputation: 118865

Silverlight needs to rendezvous with the UI thread in order to do the web request, but the UI thread is blocked on the WaitOne call, so you have a deadlock. (This can be construed as a Silverlight "feature".)

Upvotes: 5

Related Questions