Question

I want to change a Form control property from a process thread event fire in a class, I have the following code but I received this exception:

the calling thread cannot access this object because a different
thread owns it.

Code:

public partial class main : Window
{        
   public main()
   {
      InitializeComponent();
   }

   public void change()
   {
      label1.Content = "hello";
   }

   private void button1_Click(object sender, RoutedEventArgs e)
   {
      nmap nmap = new nmap(this);
      nmap.test("hello");
   }
}

class nmap
{
    private main _frm;
    private Process myprocess;

    public nmap(main frm)
    {
       _frm = frm;
    }

    public void test(object obj)
    {
        string s1 = Convert.ToString(obj);
        ProcessStartInfo startInfo = new ProcessStartInfo();
        myprocess = new Process();
        myprocess.StartInfo.FileName = "C:\\nmap\\nmap.exe";
        myprocess.EnableRaisingEvents = true;
        myprocess.Exited += new EventHandler(myProcess_Exited);

        myprocess.Start();
    }

    private void myProcess_Exited(object sender, System.EventArgs e)
    {
       try
       {
          _frm.change();
       }
       catch{}
    }
}

Please help me on this, I think delegate invoke must be work

My project is a WPF C# project.

answer is:

class nmap
    {
        private main _frm;
        private Process myprocess;


        public nmap()
        {

        }
        public nmap(main frm)
        {
            _frm = frm;
        }
        public void test(object obj)
        {
            string s1 = Convert.ToString(obj);
            ProcessStartInfo startInfo = new ProcessStartInfo();
            myprocess = new Process();
            myprocess.StartInfo.FileName = "C:\\nmap\\nmap.exe";
            //myprocess.StartInfo.CreateNoWindow = true;
            myprocess.EnableRaisingEvents = true;
            //myprocess.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
            myprocess.Exited += new EventHandler(myProcess_Exited);
            myprocess.Start();

        }

        private void myProcess_Exited(object sender, System.EventArgs e)
        {
            try
            {
                String s;
                s = "hello";
                _frm.Dispatcher.Invoke(_frm.USD, new Object[] { s });
            }
            catch{}
        }

    }

 public partial class main : Window
    {
        public delegate void UpdateStatusDelegate(string value);
        public UpdateStatusDelegate USD;

        public main()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            USD = new UpdateStatusDelegate(this.AddString);

        }
        private void AddString(String s)
        {
            label1.Content = s;

        }
        public void change()
        {
            label1.Content = "hello";
        }


        private void button1_Click(object sender, RoutedEventArgs e)
        {
            nmap nmap = new nmap(this);
            nmap.test("hello");

        }
}

Answer 1

You can not touch any UI element from any threads other than the thread that owns the object. To achieve this you can wrap the call in a Invoke method like this:

delegate void UpdateStatusDelegate (string value);

private void UpdateStatus(string value)
{
    if (InvokeRequired)
    {
        // We're not in the UI thread, so we need to call BeginInvoke
        BeginInvoke(new UpdateStatusDelegate(UpdateStatus), new object[]{value});
        return;
    }
    // Must be on the UI thread if we've got this far
    statusIndicator.Text = value;
}

in WPF world, you could get the same thing by using Dispatcher.Invoke method.