Page 376 second paragraph

[niusz]

 abstract class Canine : Animal
    {
        public bool BelongsToPack { get; protected set; } = false;

    }
}

say it has its own abstract property, BelongsToPack, but why abstract modifier didn't appear before BelongsToPack ,Thanks

[andrewstellman]

Hi! Thanks for posting this. You're right, BelongsToPack is a concrete method, because abstract classes can contain concrete methods. (Here's the reference for that – 14.2.2.2 Abstract Classes – "An abstract class is permitted (but not required) to contain abstract members.")

We could mark BelongsToPack abstract:

public abstract bool BelongsToPack { get; protected set; } = false;

But then the code wouldn't compile, because the = false; makes it an auto-implemented property, which must be concrete.

So while the book is technically correct, we definitely could do a better job teaching this part! I'm going to have to think about how to handle this—teaching about abstract classes well is challenging, so it's going to take some work to improve this, but I'm definitely going to try! We're working on the 5th edition now (targeting the next version of C#, which will probably be released in November 2023). I'll leave this issue open to track that.