This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
I assume that when you said "chars and spaces" you really meant "letters and spaces"?
Well, if you want to extend that algorithm to all letters then you're going to have to go through the Unicode code charts and find out which scripts you want to support letters from. (Hint: there's a lot of scripts covered by Unicode.)
Or you could look for code from somebody else who has already solved the problem. But if it were me I would be reviewing why somebody had required "only letters and spaces" in the first place.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com
subject: check for characters and spaces using ASCII fails for other languages