I was looking for a way to make a textbox highlight itself when clicked. Makes for easier user input when you defaulted values and saves them from having to delete them and then enter their own text. I know, rare for developers to care what the user’s experience is like. ha.
Anyway, I was just about to write my own behavior when I found this one. It was written for Silverlight 3 but works fine in Silverlight 4.
Check out his article, much more detailed than I would write.