The original poster has likely long moved on, but I took a stab at porting the Perl Geo::StreetAddress:US module used by geocoder.us to C#, dumped it on CodePlex, and think that people stumbling across this question in the future may find it useful:
US Address Parser
On the project's home page, I try to talk about its (very real) limitations. Since it is not backed by the USPS database of valid street addresses, parsing can be ambiguous and it can't confirm nor deny the validity of a given address. It can just try to pull data out from the string.
It's meant for the case when you need to get a set of data mostly in the right fields, or want to provide a shortcut to data entry (letting users paste an address into a textbox rather than tabbing among multiple fields). It is not meant for verifying the deliverability of an address.
It doesn't attempt to parse out anything above the street line, but one could probably diddle with the regex to get something reasonably close--I'd probably just break it off at the house number.
