Friday, May 29, 2009

event pseudo-field ^ hidden delegate field

-- Based on http://www.yoda.arachsys.com/csharp/events.html --
First let's review c# properties. Example - Property "age" in class Animal is really a pair of get()/set() methods manipulating a hidden realAge field. You can do anything in the get() and set(), even ignoring the realAge, or make do without the realAge variable entirely. To your clients, age appears to be a field -- a pseudofield.

An event is a pseudofield referring to a hidden delegate field. MyEvent is really a pair of add()/remove() methods to append/remove each delegate (one at a time) from the realDelegate field.

If you declare MyEvent without explicit add/remove, compiler generates them around a hidden delegate field, just like an auto-implemented property.

Compared to properties, there's some additional syntax complexity. The type of the hidden delegate field is the type mentioned after keyword "event".

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