Validating String against USPS state abbreviations

Question

I have googled this up without any luck so far, what I have to do is validate a string against the list of possible United States Postal Service state abbreviations. And, the obvious solution would be to write a code with a really lengthy if (or switch) statement that checks all the 50 states. But, as I said, it's body would have to be very lengthy. So, what is an easier way of doing the same, like maybe by using a RegEx or an enumerator object?

I'm using C# and .net 3.5 and here's the List of USPS State Abbreviations

Answer 1

This is how I'd do it:

private static String states = "|AL|AK|AS|AZ|AR|CA|CO|CT|DE|DC|FM|FL|GA|GU|HI|ID|IL|IN|IA|KS|KY|LA|ME|MH|MD|MA|MI|MN|MS|MO|MT|NE|NV|NH|NJ|NM|NY|NC|ND|MP|OH|OK|OR|PW|PA|PR|RI|SC|SD|TN|TX|UT|VT|VI|VA|WA|WV|WI|WY|";

public static bool isStateAbbreviation (String state)
{
  return state.Length == 2 && states.IndexOf( state ) > 0;
}

The method utilizes an optimized system routine, which uses a single machine instruction for doing the search. Plus, with words without fixed lengths, it is advisable to check for "|" + state + "|" so that you can ensure not hitting a substring but only a complete match. This might take some time because of the string concatenation but can still find a match without much delay. And, for validating abbreviations in lowercase as well as uppercase, you could either check state.UpperCase(), or double the string 'states' for including any lowercase variants. And, it uses the least amount of memory despite any number of runs and should seem more preferable than those Regex or Hashtable lookups every time.