There is no source information for the event.
The assumption is that since you attached the event to the connection point of the Window object, you knew which window would be the event source. When you hook the event you need to save the reference to the window in case you need the event source.
Class HTMLWindowEvents2Sink
{
public HTMLWindowEvents2Sink(IHTMLWindow2 eventSource)
{
this.eventSource=eventSource;
}
IHTMLWindow2 eventSource;
void AdviseEvent()
{
eventSource.load += this.HTMLWindow_onload;
}
....
}
You also have a performance hit and potential bug farm here, by using the delegate event handling model.