Customised business rules per customer...(asp.net mvc)
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In a web application i'm working on, items can pass through multiple states (eg. workflow) and after each workflow a rule can be run after each step which can stop the process or display additional messages. 

How should these rules be defined? 
I was thinking about a dll per rule (and hooking them up either with MEF or events) but one application could have 200-300 customers in it each with a few rules which becomes a lot of dlls.

Cheers.
