Are there really errors in the book?

Question

C++ / C#

Hello! I started studying from the book C # for schoolchildren and immediately ran into a difficulty. Namely, in the examples that are given in the book, it is not clear why everything is underlined with a red line and does not work.
Let's take this example^

Answer 1

You are writing code outside the constructor or methods of the Zoo class. Accordingly, the code is underlined. If it says so in the book, it's a mistake.