Validate String against USPS State Abbreviations

I need to be able to validate a string against a list of the possible United States Postal Service state abbreviations, and Google is not offering me any direction.

I know of the obvious solution: and that is to code a horridly huge if (or switch) statement to check and compare against all 50 states, but I am asking StackOverflow, since there has to be an easier way of doing this. Is there any RegEx or an enumerator object out there that I could use to quickly do this the most efficient way possible?

[C# and .net 3.5 by the way]

List of USPS State Abbreviations