looking for an example (MVC + multithreading)

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original post:

Quote:

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I'm looking for a c# example that shows multithreading and MVC combined.

for example: a form with two counters counting up from 0 to 100 with thread1 increasing counter1 every 100ms and thread2 increasing counter2 every 150ms.

I know the MVC pattern and I'm familiar with multithreading but I haven't worked with them alot so I'd really appreciate a simple example to show me the basic setup.

thx in advance!

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Progress:

I wrote an example code for the proposed example but can't get it to work. As sugested I used a cross thread controler to fix the thread access problem. Now I get a different error though:
"Parameter count mismatch." on line "Application.Run(new Form1());"


current code:
program.cs

Code:

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
}

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Form1.cs:

Code:

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using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form, TView
    {
        TModel model = new TModel();
        private TControler controler;

        public Form1()
        {
            InitializeComponent();

            model.addView(this);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //setup 2 threads that work to increase counters
            TControler cont = new TControler(model);
            cont.setStep(400);
            Thread thread = new Thread(new ThreadStart(cont.runme));
            thread.Name = "first";
            thread.Start();

            TControler cont2 = new TControler(model);
            cont2.setCounter(2);
            cont2.setStep(500);
            Thread thread2 = new Thread(new ThreadStart(cont2.runme));
            thread2.Name = "second";
            thread2.Start();


        }
        private delegate void CrossThreadLabelHandler(Label obj, String str);
        private void UpdateLabelText(Label obj, String str)
        {
            try
            {
                if (obj.InvokeRequired)
                    obj.BeginInvoke(new CrossThreadLabelHandler(this.UpdateLabelText), str);
                else
                    obj.Text = str;
            }
            catch(Exception e)
            {
                Console.Out.WriteLine("Exception: "+e);
            }
        }

        public void doUpdate()
        {

            UpdateLabelText(label1, model.getC1().ToString());
            UpdateLabelText(label2, model.getC2().ToString());
        }
    }

    public interface aModel
    {
        void addView(TView v);
        void removeView(TView v);
        void notifyListeners();
    }
    public class TModel : aModel
    {
        private int c1 = 0;
        private int c2 = 0;

        public void increase1()
        {
            c1++;
            notifyListeners();
        }
        public void increase2()
        {
            c2++;
            notifyListeners();
        }
        public int getC1()
        {
            return c1;
        }
        public int getC2()
        {
            return c2;
        }
       

        ArrayList l=new ArrayList();
        public void addView(TView v)
        {
            l.Add(v);
        }

        public void removeView(TView v)
        {
            l.Remove(v);
        }

        public void notifyListeners()
        {
            foreach(TView v in l)
            {
                v.doUpdate();
            }
        }
    }

    public interface TView
    {
        void doUpdate();
    }

    public interface aControler
    {
    }
    public class TControler: aControler
    {
        private TModel model;
        private volatile bool run;
        private int step=100;
        private int counter = 1;

        internal TControler(TModel m)
        {
            model=m;
            run = true;
        }
        public void setStep(int ms)
        {
            step = ms;
        }
        public void setCounter(int c)
        {
            counter = c;
        }

        public void runme()
        {
            while(run)
            {
                if(counter==1)
                    model.increase1();
                else
                    model.increase2();
                Thread.Sleep(step);
            }
        }
    }
}

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PS this is an example I built, but it doesn't work. My debugger says"Cross-thread operation not valid: Control 'label1' accessed from a thread other than the thread it was created on."

Any clues on how to fix this?

Code:

---

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form, TView
    {
        TModel model = new TModel();
        private TControler controler;

        public Form1()
        {
            InitializeComponent();

            model.addView(this);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //setup 2 threads that work to increase counters
            TControler cont = new TControler(model);
            Thread thread = new Thread(new ThreadStart(cont.runme));
            thread.Name = "first";
            thread.Start();

            TControler cont2 = new TControler(model);
            cont2.setCounter(2);
            cont2.setStep(150);
            Thread thread2 = new Thread(new ThreadStart(cont2.runme));
            thread2.Name = "second";
            thread2.Start();


        }

        public void doUpdate()
        {
            label1.Text = model.getC1().ToString();
            label2.Text = model.getC2().ToString();
        }
    }

    public interface aModel
    {
        void addView(TView v);
        void removeView(TView v);
        void notifyListeners();
    }
    public class TModel : aModel
    {
        private int c1 = 0;
        private int c2 = 0;

        public void increase1()
        {
            c1++;
            notifyListeners();
        }
        public void increase2()
        {
            c2++;
            notifyListeners();
        }
        public int getC1()
        {
            return c1;
        }
        public int getC2()
        {
            return c2;
        }
       

        ArrayList l=new ArrayList();
        public void addView(TView v)
        {
            l.Add(v);
        }

        public void removeView(TView v)
        {
            l.Remove(v);
        }

        public void notifyListeners()
        {
            foreach(TView v in l)
            {
                v.doUpdate();
            }
        }
    }

    public interface TView
    {
        void doUpdate();
    }

    public interface aControler
    {
    }
    public class TControler: aControler
    {
        private TModel model;
        private volatile bool run;
        private int step=100;
        private int counter = 1;

        internal TControler(TModel m)
        {
            model=m;
            run = true;
        }
        public void setStep(int ms)
        {
            step = ms;
        }
        public void setCounter(int c)
        {
            counter = c;
        }

        public void runme()
        {
            while(run)
            {
                if(counter==1)
                    model.increase1();
                else
                    model.increase2();
                Thread.Sleep(step);
            }
        }
    }
}

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I don't have any experience with the MVC pattern, but check out the Control.InvokeRequired property (and of course the Control.Invoke() method) to use controls from a different thread.

The problem is you can't update GUI controls outside the GUI (main) thread. So this...

Code:

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label1.Text = "test";

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...will throw the exception you're receiving.

The way around it is to call the Invoke() or BeginInvoke() methods contained within the label controls. So you'd create a method, eg...

Code:

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private delegate void CrossThreadLabelHandler(Label obj, String str);
private void UpdateLabelText(Label obj, String str)
{
    if (obj.InvokeRequired)
        obj.BeginInvoke(new CrossThreadLabelHandler(this.UpdateLabelText), str);
    else
        obj.Text = str;
}

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...and then use that method to access the GUI thread from your worker thread.

Code:

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label1.Text = "test"; // doesn't work from a different thread!!
UpdateLabelText(label1, "test"); // this will work.

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I updated my code:

Code:

---

        private delegate void CrossThreadLabelHandler(Label obj, String str);
        private void UpdateLabelText(Label obj, String str)
        {
            if (obj.InvokeRequired)
                obj.BeginInvoke(new CrossThreadLabelHandler(this.UpdateLabelText), str);
            else
                obj.Text = str;
        }

        public void doUpdate()
        {

            UpdateLabelText(label1, model.getC1().ToString());
            UpdateLabelText(label2, model.getC2().ToString());
        }

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but now I get this error: "Parameter count mismatch." on line "Application.Run(new Form1());"

I found the bug! I modified the supplied delegate/invoke code to this:

Code:

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        private delegate void CrossThreadLabelHandler(Label obj, String str);
        private void UpdateLabelText(Label obj, String str)
        {
            try
            {
                CrossThreadLabelHandler ch = new CrossThreadLabelHandler(this.UpdateLabelText);
                if (obj.InvokeRequired)
                    obj.BeginInvoke(ch, obj, str);
                else
                    obj.Text = str;
            }catch(Exception e)
            {
                Console.Out.WriteLine("Exception: "+e);
            }
        }

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Oops, sorry about that. Tired eyes is my excuse lol. :D

Code:

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obj.BeginInvoke(new CrossThreadLabelHandler(this.UpdateLabelText), obj, str);

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