In one of his articles on
building a CAB-like infrastructure, Jeremy
brought out a pretty interesting point: The choice between using Events/Delegates
and Direct Method Calls. This can be a controversial topic at hand, but it’s an interesting
aspect, and can significantly affect the readability of the code.

Events and delegates are very powerful features I use all the time. However, here’s
a tip: Be careful about building an entire framework or complex structure based purely
around delegate calls. I’ve been spending a lot of time the past few days tracing,
debugging and running through the code in the Base Adapter sample code in the BizTalk
Server 2004 SDK [1], which is exactly a little framework for building BizTalk Adapters.

Now, the base adapter is OK, in that it does make it a bit faster to develop adapters
by taking care of a lot of the boilerplate code necessary. However, a significant
part of it is built out of classes that use a lot of delegates (not even proper events,
unfortunately) to notify of significant events around each other; like for example
that a batch was submitted to BizTalk or that a message needs to be suspended.

The unfortunate side effect of this is that tracing the base adapter code in source
code form requires a lot of patience and a lot of Find References/Find Definition
jumps all around to figure out exactly what’s going on. In fact, I’ve spent quite
a few hours on it and the code can be significantly convoluted; and parts of it are
just a lot easier to trace using Step Though/Step Into in the debugger; which is rather

So next time you want to build a framework or library and think gluing all together
with delegates and events is cool; make sure you’ve got a real use case for them and
that they are not going to end up hindering readability and maintainability.

[1] The version included in the BizTalk 2006 SDK is different and
a lot simpler. I still don’t quite like it and generally prefer to write directly
against the Adapter Framework APIs, but that’s just me.

tags: BizTalk, Base
, Delegates