Don on XML API’s

I watched Don’s MSDN TV talk on passing XML around within a managed application. The value of XPathNavigaor has been discussed in blogsphere, but it was nice to see it explained by the master.

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It reminded my of one of my first encounters with Don. I was a recent addition to MCS in SoCal and we were having a team meeting / training at DevelopMentor. Among other speakers, Don was scheduled to discuss the then-brand-new SOAP spec. As is expected with Don, the presentation started with thirty minutes of “look what cool code I whipped up at 3am this morning”. In this case, the code was a COM based SAX parser based on expat. In his implementation, Don had mirrored the SAX API exactly, including providing the setXxxHandler methods. I asked him why he hadn’t used COM Events. He commented that I had really drunk the kool-aid and that was the end of it.

Personally, I hate registration API’s like SAX’s setXxxHandler methods. While COM Events has a lot of plumbing overhead to get nailed up, but the benefit was that it provided a late bound mechanism for locating event sources. Using registration API’s like setXxxHandler means having to redefine your interface to support new event types. Of course, CLR delegates, the pull model XmlReader and XPathNavigator have made the registration API vs. COM events discussion moot.

Interesting follow up to this story: I ran into Don at an internal event last November. He couldn’t remember my name, but he remembered the event at DM and that I was the one who asked about that COM events stuff.