Silverlight, Updating the UI during processing

Question

Hi, I have a simple silverlight multifile upload application, and i want to provide the user with some feedback, right now its only in a test phase and i dont have the webservice. Somehow i cant get the ui to update:

private void DoUpload()
    {
        foreach (UploadFile file in fileInfos)
        {
            int BUFFERSIZE = 1024;
            int offset = 0; //get from webservice, when partial file
            FileStream s = file.FileInfo.OpenRead();
            byte[] buffer = null;
            long remainingBytes = s.Length - offset;
            while (remainingBytes > 0)
            {
                if (remainingBytes < BUFFERSIZE)
                {
                    buffer = new byte[remainingBytes];
                    BUFFERSIZE = (int)remainingBytes;
                }
                else if (remainingBytes > BUFFERSIZE)
                {
                    buffer = new byte[BUFFERSIZE];
                }

                s.Read(buffer, 0, BUFFERSIZE);
                //push to webservice
                offset += BUFFERSIZE;
                int newPercentage = offset / (int)file.FileInfo.Length * 100;
                file.Percentage = newPercentage;
                remainingBytes = s.Length - offset;
                System.Threading.Thread.Sleep(10);
            }
            file.Percentage = 100;
            file.ImageSource = "accept.png";
        }
    }

The UploadFile is bound to the ui, so changes to this file will reflect in the UI, Problem is that all this upload takes too long (simulated it with the sleep) and during that tie UI is not getting updated, any idea on how to go about doing this?

Answer 1

I thought Silverlight only allow asynchronous calls. If you are doing things asynchronously then your use of Sleep is misleading as the upload wouldn't block the UI.

Answer 2

What you need to do is run this method on a new thread (i.e. not the UI-thread). If you block the UI thread (e.g. with a sleep), then it is blocked from updating or responding to the user in any way.

If you need to modify anything about the UI, it has to be done from the UI thread. So if you need to change the UI, and your code is running on a different thread, you can use the Dispatcher.BeginInvoke method to dispatch an operation to the UI thread. You can access the application's Dispatcher object via: Deployment.Current.Dispatcher.