C#

/// <summary>
/// Handles the parent receiving a DragOver event
/// </summary>
/// <param name="sender">The parent receiving the event</param>
/// <param name="e">Contains the data being dragged</param>
private static void _ctrlParent_DragOver(object sender, DragEventArgs e)
{
    try
    {
        // If this is a valid control for this parent, allow it to move
        // freely over, otherwise disallow DragDrop operations
        if ( DragDropHandler.CanDropHere((Control)sender, e.Data) )
        {
            // cthis... this as a Control
            Control cthis = (Control)sender;

            // Set the DragDropEffect and get the control we are dragging
            e.Effect = DragDropEffects.Move;
            Control ctrl = DragDropHandler.GetControl(e.Data, true, true);

            // If this isn't an IDragDropEnabled control don't worry about
            // showing it's position
            if (!(ctrl is IDragDropEnabled))
            {
                return;
            }

            // If this control is not part of the current "parent"
            // remove it from it's original parent and place it in
            // the current parent control collection
            if (cthis.Name != ctrl.Name)  // attempts to test for controls without the same name.
            {
                ctrl.Parent.Controls.Remove(ctrl);
                ctrl.Parent = cthis;
                cthis.Controls.Add(ctrl);
                ctrl.BringToFront();

                Point NewLocation = cthis.PointToClient(new Point(e.X, e.Y));
                ctrl.Left = NewLocation.X - dragPoint.X;
                ctrl.Top = NewLocation.Y - dragPoint.Y;
            }
            else
            {
                return;
            }
        }
        else
        {
            e.Effect = DragDropEffects.None;
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show("Error is " + ex.Message);
    }
}

private Queue<NextDataReply> packs;
private bool productionDone;

private void Enqueue(NextDataReply pack)
{
    lock (packs)
    {
        packs.Enqueue(pack);
        // Notify all threads that a new pack was enqueued
        Monitor.PulseAll(packs);
    }
}

public NextDataReply Dequeue()
{
    lock (packs)
    {
        while (packs.Count == 0 && !productionDone)
            Monitor.Wait(packs);

        // If no more data should be queued for the current item being transfered, no dequeuing is possible
        if (productionDone) return null;

        return packs.Dequeue();
    }
}