C#

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 check for same control name
                {
                    ctrl.Parent.Controls.Remove(ctrl);
                    ctrl.Parent = cthis;   // ERROR occurs here...
                    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 (System.Exception ex)
        {
            MessageBox.Show("Error is " + ex.GetBaseException());
        }
    }