System.Threading.SynchronizationContext.Current.Post(theMethod, state);
	
delegate UiSafeCall(delegate d, params object p);
void SomeUiSafeCall(delegate d, params object p)
{
  if (InvokeRequired) 
    BeginInvoke(d,p);        
  else
  {
    //do stuff to UI
  }
}
	
delegate UiSafeCall(delegate d, params object p);
void SomeUiSafeCall(delegate d, params object p)
{
  if (this.InvokeRequired) 
    this.BeginInvoke(d,p);        
  else
  {
    //do stuff to UI
  }
}
	
public class MyBackgroundThread : BackgroundWorker
{
    public event EventHandler<ClassToPassToUI> IWantTheUIToDoSomething;

    public MyStatus TheUIWantsToKnowThis { get { whatever... } }

    public void TheUIWantsMeToDoSomething()
    {
        // Do something...
    }

    protected override void OnDoWork(DoWorkEventArgs e)
    {
        // This is called when the thread is started
        while (!CancellationPending)
        {
            // The UI will set IWantTheUIToDoSomething when it is ready to do things.
            if ((IWantTheUIToDoSomething != null) && IHaveUIData())
                IWantTheUIToDoSomething( this, new ClassToPassToUI(uiData) );
        }
    }
}


public partial class MyUIClass : Form
{
    MyBackgroundThread backgroundThread;

    delegate void ChangeUICallback(object sender, ClassToPassToUI uiData);

    ...

    public MyUIClass
    {
        backgroundThread = new MyBackgroundThread();

        // Do this when you're ready for requests from background threads:
        backgroundThread.IWantTheUIToDoSomething += new EventHandler<ClassToPassToUI>(SomeoneWantsToChangeTheUI);

        // This will run MyBackgroundThread.OnDoWork in a background thread:
        backgroundThread.RunWorkerAsync();
    }


    private void UserClickedAButtonOrSomething(object sender, EventArgs e)
    {
        // Really this should be done in the background thread,
        // it is here as an example of calling a background task from the UI.
        if (backgroundThread.TheUIWantsToKnowThis == MyStatus.ThreadIsInAStateToHandleUserRequests)
            backgroundThread.TheUIWantsMeToDoSomething();

        // The UI can change the UI as well, this will not need marshalling.
        SomeoneWantsToChangeTheUI( this, new ClassToPassToUI(localData) );
    }

    void SomeoneWantsToChangeTheUI(object sender, ClassToPassToUI uiData)
    {
        if (InvokeRequired)
        {
            // A background thread wants to change the UI.
            if (iAmInAStateWhereTheUICanBeChanged)
            {
                var callback = new ChangeUICallback(SomeoneWantsToChangeTheUI);
                Invoke(callback, new object[] { sender, uiData });
            }
        }
        else
        {
            // This is on the UI thread, either because it was called from the UI or was marshalled.
            ChangeTheUI(uiData)
        }
    }
}