Question

Hy!

I can’t access listbox.InvokeRequired

Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Threading;

namespace PrimeNumbers
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private delegate void AddListItem(string item);
        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)
                    {
                        if (
                        lbPrimes.Items.Add(currval.ToString());
                    }
                }
                currval++;
            }
        }
        private void AddListBoxItem(string item)
        {
            if (this.lbPrimes.InvokeRequired) //Error: Expression to evaluate
            {

            }
        }

    }
}

Please help!

Answer 1

InvokeRequired is a winforms thing. For WPF, you’ll have to use Dispatcher. Check out this post that explains it all.