Promoted VS. Written properties into message context

[quote user="tomasr"]Only promoted properties are used for message routing inside the MsgBox (i.e. only promoted properties are considered when evaluating subscription predicates). I haven't looked at the internal implementation, but an educated guess might say that the difference between the two on the object model itself is probably just a flag set or maybe they are kept in separate property collections, but probably not much else. The interesting part all happens in the MsgBox in sql server 🙂
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Actually I believe you are spot on.  If I remember correctly, I read somewhere that each written context property also has an IsPromoted (or similar) boolean variable.  If it's true, then the property is considered promoted and available for routing/subscription matching, else it is considered as just written to the message context.

I look at it this way: the values of written context properties are available to your orchestrations and custom pipeline components; promoted properties have the same features as written properties but have the added benefit of being able to be used for subscription fulfillment.