The properties on TemplateRoute for DataTokens and Defaults are now
readonly. This prevents modifying these collections in a way that
invalidates cached data, or violates thread-safety.
To do the same for constraints, this change includes a substantial refactor
of how we realize inline constraints, and moves the constraint resolver
out of the parsing phase.
This allow creates a builder for the constraint map, that will make it
easier to implement features like optional constraints, and is reusable
for anyone building their own type of routing system.
This change makes RouteValueDictionary a full IDictionary implementation
instead of a subclass of Dictionary.
Followed the patterns used in the old implementation, namely preserving
the struct-returning behavior of Keys/Values/GetEnumerator.
Kiran Challa
N. Taylor Mullen
Praburaj
Doug Bunting
Ryan Nowak
Andrew Peters