Updating GUI from other thread

Question

I'm trying to update a listbox from another thread, what is the simplest way to achieve this?

I tried Invoking the textbox, but it didn't work.

private void dowork()
{
    TcpClient client = new TcpClient();
    client.Connect("192.168.1.3", 10);
    StreamWriter writer = new StreamWriter(client.GetStream());
    StreamReader reader = new StreamReader(client.GetStream());

    JObject o = new JObject();
    o.Add("comando", 1);
    o.Add("dir", @"C:\Users\klein\Desktop\Acionamentos");
    writer.Write(o.ToString());
    writer.Flush();
    JArray array = JArray.Parse(reader.ReadToEnd());
    for (int i = 0; i < array.Count; i++)
    {
        listBox1.Items.Add(array[i]);  //update GUI from this thread
    }
}

private void button1_Click(object sender, EventArgs e)
{
    Thread t = new Thread(dowork);
    t.Start();
}

http://stackoverflow.com/questions/2367718/c-automating-the-invokerequired-code-pattern (possible duplicate) — bas, Jan 26 '13 at 23:03
possible duplicate of [How to update the GUI from another thread in C#?](http://stackoverflow.com/questions/661561/how-to-update-the-gui-from-another-thread-in-c) — AxelEckenberger, Jan 27 '13 at 22:58

score 1 · Answer 1 · answered Jan 26 '13 at 23:04

1

You can use Control.Invoke to get on UI thread and then update the list box.

However, I suggest you look at using a BackgroundWorker.

answered Jan 26 '13 at 23:04

Richard Schneider

34,944
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score 1 · Accepted Answer · edited Apr 01 '13 at 17:09

I would use a BackgroundWorker, you can do your async stuff in DoWork, report your progress using bgworker.ReportProgress() and you will get the callback in ProgressChanged (I would call ReportProgress for every element processed), then you will be able to update your GUI controls.

The worker can also fire RunWorkerCompleted when it ends.

YourType arrayitem;

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    TcpClient client = new TcpClient();
    client.Connect("192.168.1.3", 10);
    StreamWriter writer = new StreamWriter(client.GetStream());
    StreamReader reader = new StreamReader(client.GetStream());

    JObject o = new JObject();
    o.Add("comando", 1);
    o.Add("dir", @"C:\Users\klein\Desktop\Acionamentos");
    writer.Write(o.ToString());
    writer.Flush();
    JArray array = JArray.Parse(reader.ReadToEnd());

    int percentage;

    for (int i = 0; i < array.Count; i++)
    {
        arrayitem = array[i];
        percentage = ((i + 1)*100)/array.Count;
        backgroundWorker1.ReportProgress(percentage);
    }
}

private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    listBox1.Items.Add(arrayitem);
    progressBar1.Value = e.ProgressPercentage; // in case you'd want to add a progressbar
}

private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    label1.Text = "Done";
}

Keep in mind your backgroundworker must have true in the WorkerReportProgress property.

Do you have any examples on this approach? – Bruno Klein Jan 26 '13 at 23:15 — Bruno Klein, Jan 26 '13 at 23:15

score 1 · Answer 3 · edited Apr 01 '13 at 17:07

1

You need to use Dispatcher.BeginInvoke. You can check this link to have better understanding on how to update the UI controls from different thread. For example, if the listbox is named listbox1

for (int i = 0; i < array.Count; i++)
{
    listBox1.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal,
        new Action(delegate() { listBox1.Items.Add(array[i]) });
}

edited Apr 01 '13 at 17:07

Michael Celey

12,645
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answered Jan 28 '13 at 06:26

akshayb

76
6

Updating GUI from other thread

3 Answers3

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