求高手帮助，看个程序，不知道为什么错误？？

private void menuItem4_Click(object sender, System.EventArgs e)
{
            ThreadStart threadStart = new ThreadStart(CreateGraph);
            Thread thread = new Thread(threadStart);
            thread.Start();
            //CreateGraph(); }
        private void CreateGraph()
        {
            MapInfo.Mapping.FeatureLayer nodeLayer = (MapInfo.Mapping.FeatureLayer)this.mapControl1.Map.Layers["Nliaoning"];
            MapInfo.Mapping.FeatureLayer lineLayer = (MapInfo.Mapping.FeatureLayer)this.mapControl1.Map.Layers["Rliaoning"];
            graph = new Graph(nodeLayer, lineLayer);
            long l = DateTime.Now.Ticks;
            graph.ConstructGraph();
            l = (DateTime.Now.Ticks - l) / 10000;
            MessageBox.Show("构建图需要的时间是:" + l + "毫秒");
            this.hashGraph = graph.HashGraph;
            graph.NodeLoop();
            this.nodeCount = graph.NodeCount;
            this.nodeName = graph.NodeName;
            this.nodeI = graph.NodeI;
        }
   
上面的CreateGraph()放到主线程中运行没有错误，但是放到一个新建的线程里就出错，