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.
You can test the length of the string or see if the string is all space characters, or use trim to remove white space and then test the length. If the string is in one of these conditions, then don't add it to the box.