To determine whether you need to perform any one-time initialization operations the first time your application runs 确定在第一次运行应用程序时,是否需要执行任何一次性的初始化操作。
Selecting event to perform additional initialization operations that are specific to your application, to validate the values of parameters, or to change the parameter values before the 控件执行选择操作前执行特定于应用程序的附加初始化操作,可以验证参数的值,或更改参数值。