理论知识需要不断学习，不能单纯注重实践
//Map A container for the display and manipulation of map data.
//MapControl Com类
//MapControlClass .Net托管类
//axMapControl Windows窗体控件
//通过axMapControl的Object和GetOcx属性可以获取MapControlClass
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//IMap.
//Use the IMap interface to display data from various data sources.
//通过IMapControl的Map属性可以获取IMap
//The MapControl encapsulates the Map CoClass and provides additional properties, methods and events for: managing the general appearance, display properties and map properties of the control(MapControl封装了Map类，并且提供额外的属性，方法和事件，用来管理控件的一般的样式，展现属性，底图属性); adding and managing data layers within the control; loading map documents into the control; dropping data onto the control from other applications; and tracking shapes and drawing to the display.