Sorry about that. During editing the technical editors suggested some name changes and unfortunately they did not all get made in both the book and the code. I know it's frustrating and I apologize.
In general if IntelliSense can't find a symbol such as a name, the first thing to check is that the symbol actually exists. In this case (and many others) that means looking at the form or the variable declarations and making sure they are spelled the same way. It's very common for a programmer to name a control LastNameTextBox but then type LastNmeTextBox in the code and not notice the typo.
In fact, you can often avoid that problem by making IntelliSense type for you. In this example, you could type Last and then press Shift+Space to make IntelliSense list the options. Then you can select the name without needing to retype it.