#270 – Passing a Reference Type by Reference

When you pass a reference type by value to a method, you pass in a reference to the object.  The method can change the object, but can’t change the reference.

        public static void AnnotateMotto(Dog d)
            // Change the dog's motto
            d.Motto = d.Motto + " while panting";

You can also pass a reference type by reference, which means that the method can change not only the contents of the object pointed to, but change the reference, causing it to refer to a different object.

        public static void FindNewFavorite(ref Dog fav)
            fav.Motto = "No longer the favorite";

            foreach (Dog d in AllDogs)
                if (d.Motto.Contains("ball"))
                    fav = d;

Below is an example of calling this method.

            Dog kirby = new Dog("Kirby");
            kirby.Motto = "Retrieve balls";

            Dog jack = new Dog("Jack");
            jack.Motto = "Growl at people";

            Dog myFav = jack;
            Dog.FindNewFavorite(ref myFav);

            Console.WriteLine(myFav.Name);   // Kirby

About Sean
Software developer in the Twin Cities area, passionate about software development and sailing.

One Response to #270 – Passing a Reference Type by Reference

  1. Thanks Sean! I’ve not seen anyone explain why you might want to pass a reference type by reference before. I knew it was possible, because the compiler doesn’t complain about it, but I could never think of a good reason to do it before.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: