#358 – Virtual Properties Support Polymorphism

In C#, polymorphism is implemented using virtual members–which can be methods, properties, indexers or events.

A virtual property has an implementation in the base class that can be overridden in a derived class.  When the property is read or written, the get or set accessor that is used is determined at run-time based on the type of the underlying object.

A virtual property is defined in the base class using the virtual keyword.

        protected string temperament;
        public virtual string Temperament
        {
            get
            {
                return string.Format("{0} is {1}", Name, temperament);
            }
        }

A virtual property is overridden in a derived class using the override keyword.

        public override string Temperament
        {
            get
            {
                return string.Format("Terrier {0} is {1}", Name, temperament);
            }
        }

Using the property:

            Dog kirby = new Dog("Kirby", 15);
            Console.WriteLine(kirby.Temperament);  // Kirby is Average

            Dog jack = new Terrier("Jack", 15);
            Console.WriteLine(jack.Temperament);   // Terrier Jack is Surly