Question

Possible Duplicate:
The calling thread cannot access this object because a different thread owns it

Error:

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

Code:

public partial class MainWindow : Window
    {
        Thread t;
        bool interrupt;
        public MainWindow()
        {
            InitializeComponent();
        }

        private void btss_Click(object sender, RoutedEventArgs e)
        {
            if (t == null)
            {
                t = new Thread(this.calculate);
                t.Start();
                btss.Content = "Stop";
            }
            else
            {
                t.Interrupt();
            }

        }

        private void calculate()
        {
            int currval = 2;
            int devide = 2;
            while (!interrupt)
            {
                for (int i = 2; i < currval/2; i++)
                {
                    if (2 % i != 0)
                    {
                        lbPrimes.Items.Add(currval.ToString()); //Error occures here
                    }
                }
                currval++;
            }
        }
    }

What would be causing this, and how can I resolve it?

Answer 1

You need to rejoin the main UI thread in order to affect the UI. You can check whether this is needed with InvokeRequired, and implement Invoke before referencing the controls.

private void calculate()
{
    if (InvokeRequired)
    {
        Invoke(new Action(() => calculate()));
    }
    else
    {
      //
    }
 }