/// <summary> Notify listeners that the specified vertex was added.
        ///
        /// </summary>
        /// <param name="vertex">the vertex that was added.
        /// </param>
        protected internal virtual void  fireVertexAdded(System.Object vertex)
        {
            GraphVertexChangeEvent e = createGraphVertexChangeEvent(GraphVertexChangeEvent.VERTEX_ADDED, vertex);

            for (int i = 0; i < m_vertexSetListeners.Count; i++)
            {
                VertexSetListener l = (VertexSetListener)m_vertexSetListeners[i];

                l.vertexAdded(this, e);
            }

            for (int i = 0; i < m_graphListeners.Count; i++)
            {
                GraphListener l = (GraphListener)m_graphListeners[i];

                l.vertexAdded(this, e);
            }
        }