Thread and Invoke, how to modify a label?

Question

I work on an application in c# and I have a problem with my thread and my UI...

I want to add +1 on my label when the thread is running. The problem is I don't know how I can fix that... I have read a lot of "how to" but the solutions donc work with my app..

My thread class:

 class clsWorker
    {
        //Thread myThread = new Thread(new ThreadStart(ThreadLoop));

        public SerialPort port;
        public String url;
        Thread t;
        clsSMS clsobjSMS = new clsSMS();
        SMSapplication clsobjAPP = new SMSapplication();

        public clsWorker(SerialPort serialPort, String urlChamp)
        {
            this.port = serialPort;
            this.url = urlChamp;
        }


        public void StartThread()
        {   
            t = new Thread(new ThreadStart(ThreadLoop));
            t.Start();
        }


        public void ThreadLoop()
        {
             // How I can add +1 on the countSMSok label ??
             clsobjAPP.updateCountSMS("countSMSok");

        }
    }

My application class :

public partial class SMSapplication : Form
    {
public void updateCountSMS(String label)
    {
        int num;

            this.countSMSnok = new System.Windows.Forms.Label();
            this.countSMSok = new System.Windows.Forms.Label();

            this.Controls.Add(this.countSMSnok );
            this.Controls.Add(this.countSMSok );


         if (label == this.countSMSok.Name.ToString())
        {
           if (int.TryParse(this.countSMSok.Text.ToString(), out num))
                this.countSMSok.Invoke((MethodInvoker)(() => this.countSMSok.Text = num++.ToString()));

        }
        else if (label == this.countSMSnok.Name.ToString())
        {
            if (int.TryParse(this.countSMSnok.Text.ToString(), out num))
                this.countSMSnok.Invoke((MethodInvoker)(() => this.countSMSnok.Text = num++.ToString()));
        }  
    }

       private void btnRequestStart_Click(object sender, EventArgs e)
    {
        this.btnRequestStart.Enabled = false;
        this.btnRequestStop.Enabled = true;
        objclsWorker = new clsWorker(this.port, this.urlChecker.Text);
        objclsWorker.StartThread();
    }

}

Thanks you very very much for your helping !

What does "doesn't work" mean? Please post any error messages/exceptions you get. — Lennart, Mar 16 '13 at 10:50
Try adding `IntPtr tempHandle = this.Handle;` before the Invoke call. This accesses the window handle the exception complains about. — Lennart, Mar 16 '13 at 10:57
After adding 'IntPtr tempHandle = this.Handle;' before the Invoke call, a new error appear: The embedded statement can not be a statement or a labeled statement — Geoffrey, Mar 16 '13 at 11:00
Have you tried using Dispatcher (e.g.: Application.Current.Dispatcher.Invoke) — jacob aloysious, Mar 16 '13 at 11:02
I have added the StartThread() call. Sorry jacod, I'am a "nweebie" in C#... I don't know.. :) — Geoffrey, Mar 16 '13 at 11:07
Have you added the `this.countSMSok` to forms control collection? — Hamlet Hakobyan, Mar 16 '13 at 11:11
It appears from the exception that the Controls `countSMSnok` and `countSMSok` have not been initialized. — jordanhill123, Mar 16 '13 at 11:11
Yes I have added the this.countSMSok in the control collection. If I do this.countSMSok.Text = "hello" in the private void btnRequestStart_Click that's work ! But when I call directly the updateCountSMS(String label) method that's fail... — Geoffrey, Mar 16 '13 at 11:15
Possible duplicate, have you seen http://stackoverflow.com/questions/661561/how-to-update-the-gui-from-another-thread-in-c ? — Catalin M., Mar 16 '13 at 11:17
Make sure, you have any other call of `updateCountSMS` before `InitializeComponent()`. — Hamlet Hakobyan, Mar 16 '13 at 11:22
Nice jordanhill123 ! Now the application don't bug, but my label are not actualized... Si the edit please :) — Geoffrey, Mar 16 '13 at 11:32

score 0 · Answer 1 · answered Mar 16 '13 at 11:14

0

Make sure you create an instance of the label and add the label to the Controls

    this.countSMSnok = new System.Windows.Forms.Label();
    this.countSMSok = new System.Windows.Forms.Label();

    this.Controls.Add(this.countSMSnok );
    this.Controls.Add(this.countSMSok );

answered Mar 16 '13 at 11:14

jordanhill123

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Nice jordanhill123 ! Now the application don't bug, but my label are not actualized... Si the edit please :) – Geoffrey Mar 16 '13 at 11:28

Grzegorz W · Answer 2 · 2013-03-16T11:46:25.120

You can not initialize new object of SMSapplication class, update it and expect it to update your first form. Those are different 'things'. Also You should use SynchronizationContext instead of invoke.

Here's working code:

Form:

public partial class SMSapplication : Form
{
    private SynchronizationContext context = null;
    private SerialPort port;

    public SMSapplication()
    {
        InitializeComponent();
        this.countSMSok.Text = "0";
        this.context = WindowsFormsSynchronizationContext.Current;
    }

    public void updateCountSMS(String label)
    {
        this.context.Post(new SendOrPostCallback(updateCountSMSSync), label);
    }

    private void updateCountSMSSync(object o)
    {
        string label = o as string;
        int num;

        if (label == this.countSMSok.Name.ToString())
        {
            if (int.TryParse(this.countSMSok.Text.ToString(), out num))
            {
                this.countSMSok.Text = (++num).ToString();
            }
        }
    }

    private void btnRequestStart_Click(object sender, EventArgs e)
    {
        clsWorker objclsWorker = new clsWorker(this, this.port, this.urlChecker.Text);
        objclsWorker.StartThread();
    }
}

And worker:

class clsWorker
{
    public SerialPort port;
    public String url;
    SMSapplication clsobjAPP = null;

    public clsWorker(SMSapplication app, SerialPort serialPort, String urlChamp)
    {
        this.clsobjAPP = app;
        this.port = serialPort;
        this.url = urlChamp;
    }

    public void StartThread()
    {
        new Thread(new ThreadStart(ThreadLoop)).Start();
    }


    public void ThreadLoop()
    {
        clsobjAPP.updateCountSMS("countSMSok");
    }
}

Hooooo my good, you are a good ! That's work perfectly! I have understand my stupidity. I created an new instanciation... Thanks to you, I will sleep less stupid :) !! Thanks you +++ — Geoffrey, Mar 16 '13 at 12:11

Thread and Invoke, how to modify a label?

2 Answers2