Hook？

 public interface IHook
    {
        /// <summary>
        /// 二维地图控件对象
        /// </summary>
        ESRI.ArcGIS.Controls.IMapControl4 MapControl { get; set; }

     }

 public class HookHelper: IHook
    {
        private static HookHelper mHookHelper = null;

        private HookHelper() { }

        public static HookHelper GetInstance()
        {
            if (mHookHelper == null)
            {
                mHookHelper = new HookHelper();
            }

            return HookHelper;
        }

        public IEventAggregator EventAggregator { get; set; }

        public ESRI.ArcGIS.Controls.IMapControl4 MapControl { get; set; }

        public ESRI.ArcGIS.Carto.IMap Map { get; set; }
}

从一个黑箱中有引n条线。