My users keep finding little issues with out 'Site Admin' pages - they want to do crazy things like type large numbers with 'thousands' seperators and/or decimail points, ie. 12,500 and 3,500.99
Of course, in my testing I only type 1233465 or 99999 so I never see the Exceptions thrown by their "bad" input.
This page is a handy reference for all things format-related, including both ToString() output as well as parsing inputs : Inside C#, Second Edition: String Handling and Regular Expressions Part 1.
The answer to my problem is here too - Int32.Parse(string, NumberStyles) with the System.Globalization.NumberStyles enum to pick and choose what inputs are acceptable. You might still want a try/catch, or some Regex Validation on the client side, just to make sure...