C#: Stop a main thread from running

Question

2.00/5 (3 votes)

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How can I stop the main thread that is running on my application? I have three classes: the first class is in the main form, the second is a user control that has a button in it with an image, and the last thread is the class that contains a code that keeps on changing the icon of the button in the class usercontrol.

So as long as the main window is open, the thread just keeps on invoking the class usercontrol and the usercontrol class that contains the "main thread" calls the third Class.

The problem is when I close my main form, I notice that my main thread is still running. How can I close the main thread when I close my main form?

Sample code:

/* This is the Main form that is being displayed and it contains a flowlayout */

public Main(){

  InitializeComponent();
/* a flowlayoutpanel attached at the main form */
            flowLayoutPanel1.AutoScroll = true;
            flowLayoutPanel1.Dock = DockStyle.Fill;
            for (int i = 0; i < 10; i++)
            {
                //flowLayoutPanel1.Controls.Add(createButton((i+1) + ""));
                flowLayoutPanel1.Controls.Add(new Monitor());
            }


}
/*End of main form */





/* This is my 2nd class which is a usercontrol class */

public partial class Monitor : UserControl
    {
        check chk = new check();
        public static Thread thread;
        public Monitor()
        {
            InitializeComponent();
            thread = new Thread(chk.changecolor);
            chk.getButton = this.button1;
            thread.Start();            
     
        }
 
  
        private void button1_Click(object sender, EventArgs e)
        {
            chk.isChange = true;
        }
    }




/* This is the 3rd class that handles the changing of the button icons in the 2nd class (the usercontrol class) */

class check
    {
        bool t = false;
        bool change = false;
        Button b;
        public void changecolor() {
         //   btn.Image = global::Practice.Properties.Resources.Untitled_1;
            while(true){
                Console.WriteLine("ahha");
                if (t)
                {
                    if (change)
                    {
                     b.Image = global::CafeMonitorSystem.Properties.Resources.logon;
                        change = false;
                    }
                    else
                    {
                b.Image = global::CafeMonitorSystem.Properties.Resources.Untitled_1;
                        change = true;
                    }
                }
                Thread.Sleep(300);
            }
       
     
        }
        public bool isChange {
            get{ return t;}
            set{ 
             t= value;
             change = value;
            }
        }
        public Button getButton {
            get {return b;}
            set {b = value;}        
        }      
    }

So the problem is the UserControl class that contains the "Main Thread". It keeps on running even when the main form is closed.

How can I terminate it when I close the form?

Any help is greatly appreciated.

Posted 4-Apr-11 23:59pm

Madzmar25

Updated 5-Apr-11 0:07am

Slacker007

v2

Add a Solution

3 solutions

Solution 2

Use Application.Exit[^] method for closing the application.

Posted 5-Apr-11 0:43am

J a a n s

Comments

SwitcherSoft 5-Apr-11 7:11am

This will not help, as the secondary thread will still be running. Except of course if you set it to be a background thread.

Manfred Rudolf Bihy 5-Apr-11 8:39am

course instead of coarse!
FTFY

SwitcherSoft 5-Apr-11 9:55am

Thanks =)

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SwitcherSoft · Accepted Answer · 2011-04-05T01:05:00

Your secondary threads are still running and the main thread will only exit once these thread(s) have finished what they needed to do.

Because you have infinite loop while (true)... that thread will never exit so you will need to stop it.

Here is some code to stop it.

C#

public partial class Monitor : UserControl
    {
        check chk = new check();
        public static Thread thread;
        public Monitor()
        {
            InitializeComponent();
            thread = new Thread(chk.changecolor);
            chk.getButton = this.button1;
            thread.Start();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            chk.isChange = true;
        }

    //HERE IS THE STOP CODE
     public void StopThread()
     {
        //this will let the thread exit gracefully
        chk._CanRun = false;
     }
    }

Also, you need to change your infinite loop

try something like this

class check
    {
        bool t = false;
        bool change = false;
        public bool _CanRun = true;//HERE ADDED THIS
        Button b;
        public void changecolor() {
         //   btn.Image = global::Practice.Properties.Resources.Untitled_1;
           
            while (_CanRun)
            {
                //do what you need todo

               
                Thread.Sleep(300);//here you could use AutoResetEvent with the Set method to avoid
                                  //having to wait, you can also use Thread.Abort but that will cause an 
                                  //exception
            }
       
     
        }
        public bool isChange {
            get{ return t;}
            set{ 
             t= value;
             change = value;
            }
        }
        public Button getButton {
            get {return b;}
            set {b = value;}        
        }      
    }

This will let the thread exit gracefully.

Here you should call the stopThread from the main from

C#

//you should add this using
        //using System.Collections.Generic;
        private List<monitor> MonitorList = new List<monitor>();

            /* This is the Main form that is being displayed and it contains a flowlayout */
        public Main()
        {
            InitializeComponent();

            
            //this event can be added using your property tab/events of the form.
            this.FormClosing += new System.Windows.Forms.FormClosingEventHandler(Main_FormClosing);


            /* a flowlayoutpanel attached at the main form */
            flowLayoutPanel1.AutoScroll = true;
            flowLayoutPanel1.Dock = DockStyle.Fill;

            Monitor oMonitorTemp = null;

            for (int i = 0; i < 10; i++)
            {
                oMonitorTemp = new Monitor();

                //flowLayoutPanel1.Controls.Add(createButton((i+1) + ""));
                flowLayoutPanel1.Controls.Add(oMonitorTemp);

                //adding to list to be able to keep track of all objects
                //you can also go through all the controls in flowLayoutPanel1 
                //and check which ones are of type Monitor
                MonitorList.Add(oMonitorTemp);

            }


        }

        private void Main_FormClosing(object sender, FormClosingEventArgs e)
        {
            foreach (Monitor mon in MonitorList)
            {
                mon.StopThread();
            }

        }
/*End of main form */
</monitor></monitor>

You should also look at AutoResetEvent

Try this link -> http://msdn.microsoft.com/en-us/library/system.threading.autoresetevent.aspx[^]

Regards

Terence

Olivier Levrey · Accepted Answer · 2011-04-05T00:07:00

Solution 1

Do this before starting the thread:

C#

thread.IsBackground = true;

From MSDN: Background threads are identical to foreground threads, except that background threads do not prevent a process from terminating.
http://msdn.microsoft.com/en-us/library/system.threading.thread.isbackground.aspx[^]

But be careful about your thread function. You shouldn't change or use any UI controls from a different thread. Have a look to InvokeRequired, Invoke and BeginInvoke.

Posted 5-Apr-11 0:07am

Olivier Levrey

Updated 5-Apr-11 1:54am

v2

Comments

Madzmar25 5-Apr-11 6:19am

What do you mean i shouldnt change or use any UI controls in different thread?

Olivier Levrey 5-Apr-11 6:24am

You can't change them directly. Instead of writing b.Image = ... in your thread function, you should write something like b.Invoke((Action)(() => b.Image = ...));.
The Invoke (or BeginInvoke) methods execute a function on the proper thread (the one which created the control).

Madzmar25 5-Apr-11 6:20am

Well this thread is responsible for changing the property of the button in the 2nd class or the UserControl class... it changes its icon image...

Olivier Levrey 5-Apr-11 6:25am

Have a look to that page for example: http://msdn.microsoft.com/en-us/library/ms171728(v=vs.80).aspx

SwitcherSoft 5-Apr-11 8:08am

This will solve it, only make a thread background if it does not do any critical operation. vote of 5 from me Olivier

Olivier Levrey 5-Apr-11 8:14am

Thank you.

Manfred Rudolf Bihy 5-Apr-11 8:38am

Agreed 5+!