在关于c#的书中关于事件的章节中有代码示例:
class CountDown
{
private uint _seconds;
public CountDown(uint seconds)
{
_seconds = seconds;
}
public void Start()
{
new Thread(() =>
{
uint n = _seconds;
while (n > 0u)
{
var tick = Tick; ///??????
if (tick != null)
tick(n);
Thread.Sleep(1000);
n--;
}
var finished = Finished; ///??????
if (finished != null)
finished();
}).Start();
}
}
public event Action<uint> Tick;
public event Action Finished;
创建事件的本地副本(勾选和完成)并通过它引发事件的原因是什么?这是常见的做法并且有一定的意义吗?我试过,但无法从书中得到它。