C#

public partial class Form1 : Form
    {
        public delegate int SomeMethod();

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //AddToList(IntFetcher.SlowFetch());
            SomeMethod method = IntFetcher.SlowFetch;
            method.BeginInvoke(EndFetchInt, method);
        }

        public void EndFetchInt(IAsyncResult result)
        {
            SomeMethod method = result.AsyncState as SomeMethod;
            int i = method.EndInvoke(result);
            MethodInvoker mi = new MethodInvoker(this.AddToList);
            this.BeginInvoke(mi, i);
        }
        
        public void AddToList()
        {
            int i = 0;
            ListViewItem lvi = new ListViewItem();
            lvi.Text = i.ToString();
            lvi.SubItems.Add(DateTime.Now.ToString());
            listView1.Items.Add(lvi);
        }

        public void AddToList(int data)
        {
            ListViewItem lvi = new ListViewItem();
            lvi.Text = data.ToString();
            lvi.SubItems.Add(DateTime.Now.ToString());
            listView1.Items.Add(lvi);
        }

    }

    public static class IntFetcher
    {
        public static int SlowFetch()
        {
            // Simulate a slow i/o process
            Thread.Sleep(3150); 
            Random random = new Random(DateTime.Now.Millisecond);
            return random.Next(100, 500);
        }
    }