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Code run - after instantiate GUI-Controls in Thread - is not executed ???

Posted on 2009-05-10
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Last Modified: 2012-05-06
Hello

I have 2 Form. In the MainWindow I start a thread which creates the second Form -ProgressWindow - and I try to set a value in the ProgressBar but nothings happens, WHY?

I get no exception just nothing happens after the Dialog is shown.
FORM_1:
 

public partial class MainWindow : Form

    {

        public MainWindow()

        {

            InitializeComponent();

        }
 

        private void button1_Click(object sender, EventArgs e)

        {

            var myThread = new Thread(Calculate_Tread);

            myThread.Start();

        }
 

        public void Calculate_Tread()

        {

            var myProgressWindow = new ProgressWindow();

            myProgressWindow.ShowDialog();

            Console.WriteLine("code after ShowDialog");

            myProgressWindow.SetValue(80);
 

        }

    }
 

FORM_2:
 

public partial class ProgressWindow : Form

    {

        public ProgressWindow()

        {

            InitializeComponent();

        }
 

        public void SetValue(int value)

        {

            progressBar1.Value = value;

        }

    }

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Question by:MSFanboy
  • 3
4 Comments
 
LVL 4

Expert Comment

by:somnatic
ID: 24349056
Might be because you are calling a GUI object from within another thread (though you whould get an exception). Try using a BackgroundWorker and the according events.
0
 

Author Comment

by:MSFanboy
ID: 24349786
I call the GUI object from the thread it was created so there should NOT be a problem and if there would be the typical problem I would get such a message:
"The calling thread cannot access this object because a different thread owns it."

But I did NOT get such a message! To make sure 100% I even invoked the whole creation of the progresswindow object and there is no difference...
Backgroundworker sucks and I have already implemented my threads so I do NOT want to refactor whole code. Til now I havent had any problems with gui access and threads only now its the first time that I have outsourced my progressbar in another Form instead of using the progressBar in the Form where the thread runs.
0
 

Author Comment

by:MSFanboy
ID: 24352948
one thing I found out is that form.ShowDialog() is blocking the thread somehow because if I use form.Show() the code after its call is executed.
Someone knows more?
0
 

Accepted Solution

by:
MSFanboy earned 0 total points
ID: 24371890
above is my solution

using System;

using System.Threading;

using System.Windows.Forms;
 

namespace ThreadTest

{

    public partial class MainWindow : Form

    {

        /// <summary>

        /// Hält eine Instanz der Progressform-Klasse zur

        /// Darstellung während des Longrunning-Task.

        /// </summary>

        private ProgressWindow progressForm;
 
 

        /// <summary>

        /// Delegate um die ProgressForm Thread-safe zu schliesen

        /// </summary>

        delegate void CloseDialogCallback();
 
 

        public MainWindow()

        {

            InitializeComponent();

            this.progressForm = new ProgressWindow();
 
 

          

        }  
 

        /// <summary>

        /// Dummy-Job

        /// </summary>

        /// <param name="obj">

        /// Dummy-Objekt um ParameterizedThreadStart zu simulieren.

        /// </param>

        private void DoSomething(object obj)

        {

           

            {

                // 3 Sekunden im Kreis fahren

                int counter = 0;

                while (counter < 100)

                {

                    Thread.Sleep(100);

                    counter++;
 

                   this.IncreaseProgressBar();

                }

            };

                
 
 

            // Kreisfahrt fertig, Progressfenster schliesen

            this.CloseDialog();

        }
 

        private void IncreaseProgressBar()

        {

            // prüfen ob von unterschiedlichen Threads aufgerufen wird

            if (this.progressForm.InvokeRequired)

            {

                // Threads unterschiedlich, Delegaten initialisieren

                CloseDialogCallback callBack = new 

CloseDialogCallback(this.IncreaseProgressBar);
 
 

                // Delegaten asynchron, im Kontext des UI-Thread, aufrufen

                this.Invoke(callBack);

            }

            else

            {

                // jetzt asynchron im UI-Kontext das Progressfenster 

schliesen.

                this.progressForm.IncreaseValue();

            }

        }
 
 

        /// <summary>

        /// Schliest das Progress-Fenster Thread-safe

        /// </summary>

        private void CloseDialog()

        {

            // prüfen ob von unterschiedlichen Threads aufgerufen wird

            if (this.progressForm.InvokeRequired)

            {

                // Threads unterschiedlich, Delegaten initialisieren

                CloseDialogCallback callBack = new 

CloseDialogCallback(this.CloseDialog);
 
 

                // Delegaten asynchron, im Kontext des UI-Thread, aufrufen

                this.Invoke(callBack);

            }

            else

            {

                // jetzt asynchron im UI-Kontext das Progressfenster 

schliesen.

                this.progressForm.Close();

            }

        }
 

        private void button1_Click(object sender, EventArgs e)

        {

            // erst den longrunning Thread starten da die Progressform 

das UI blockiert.

            var thread = new Thread(this.DoSomething);

            thread.Start(new object());
 
 

            // Progressform anzeigen

            this.progressForm.ShowDialog(this);

        }

    }

}

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