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();
}

stackoverflow.com/questions/2367718/… (possible duplicate) — bas
– bas, Commented Jan 26, 2013 at 23:03
possible duplicate of How to update the GUI from another thread in C#? — AxelEckenberger
– AxelEckenberger, Commented Jan 27, 2013 at 22:58

Michael Celey · Accepted Answer · 2013-04-01 17:09:41Z

1

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.

edited Apr 1, 2013 at 17:09

Michael Celey

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answered Jan 26, 2013 at 23:13

user1162766

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2 Comments

Bruno Klein Over a year ago

Do you have any examples on this approach?

user1162766 Over a year ago

I added one example, hope it helps.

Richard Schneider · Accepted Answer · 2013-01-26 23:04:30Z

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, 2013 at 23:04

Richard Schneider

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Comments

Michael Celey · Accepted Answer · 2013-04-01 17:07:31Z

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 1, 2013 at 17:07

Michael Celey

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answered Jan 28, 2013 at 6:26

akshayb

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