WPF C#

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="WPF" Height="200" Width="300"
    Loaded="Window_Loaded">
    
        One Million Numbers:
        
    


//File:Window.xaml.cs
using System.Windows;
using System.Windows.Threading;
using System.Collections.Generic;
namespace WpfApplication1
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
        }
        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            this.Dispatcher.BeginInvoke(DispatcherPriority.Background,new LoadNumbersDelegate(LoadNumbers));
        }
        private delegate void LoadNumbersDelegate();
        private void LoadNumbers()
        {
            List numberDescriptions = new List();
            for(int i = 1; i <= 1000000; i++)
            {
                numberDescriptions.Add("Number " + i.ToString());
            }
            listBox.ItemsSource = numberDescriptions;
        }
    }
}