Welcome to the Lounge

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public static void GetLanMachinesThreaded(System.Windows.Threading.Dispatcher dispatcher, 
                                          List<HostAddress> subnet, 
                                          Control control, 
                                          bool setItemsSource=false)
{
    List<Task> tasks = new List<Task>();
    foreach(HostAddress item in subnet)
    {
        var t = Task.Factory.StartNew(() => { item.FindHost(); });
        tasks.Add(t);
    }
    Task.Factory.ContinueWhenAll(tasks.ToArray(), result =>
    {
        subnet.RemoveAll(item => item.Host == null || item.Shares.Count == 0);
        if (control != null)
        {
            if (control is ItemsControl && setItemsSource)
            {
                dispatcher.BeginInvoke(new Action(() => ((ItemsControl)control).ItemsSource = subnet));
            }
            dispatcher.BeginInvoke(new Action(() => control.Focus()));
        }
    });
}