crawler.StatusChanged(crawler, null)代码到底做什么用？

[老鱼趣多多]

请问，下面这段话的含义究竟是想做什么？我读不懂。。。
crawler.StatusChanged(crawler, null);



关键代码部分如下：

public delegate void CrawlerStatusChangedEventHandler(object sender, CrawlerStatusChangedEventArgs e);
public class CrawlerStatusChangedEventArgs : EventArgs
{
public CrawlerStatusChangedEventType EventType
{
get;
set;
}
}

public event CrawlerStatusChangedEventHandler StatusChanged;

[haa17]

http://msdn.microsoft.com/zh-cn/library/system.workflow.componentmodel.activity.statuschanged.aspx