在衍生类别中覆写时，报告物件如何使用内容型别中的栏位和属性。
When overridden in a derived class, reports on how the object USES fields and properties in the context type.
使用的值必须从提供给衍生类别建构函式的引数中判断。
The values that are used must be determined from the arguments supplied to the derived class constructor.
虽然有时您可能会想要使用只能由基底类别所引发的事件，但是在多数情形下，您应该启用衍生类别来叫用基底类别事件。
Although sometimes you may want an event that can only be raised by the base class, most of the time, you should enable the derived class to invoke base class events.
应用推荐