#448 – Use the is Operator to See if an Object Implements an Interface

We saw that we could use the as operator to cast an object to a variable of a particular interface type.  If the object’s type does not implement the interface, the as operator returns null.

            IMoo viaMoo = objSomething as IMoo;
            if (viaMoo != null)
                viaMoo.Moo();

You can also use the is operator to first check to see if an object’s class implements a particular interface.

        private static void MooIfYouCan(object mooCandidate)
        {
            IMoo viaMoo;
            if (mooCandidate is IMoo)
            {
                viaMoo = (IMoo)mooCandidate;
                viaMoo.Moo();
            }
        }

We can pass any object into this method and the IMoo.Moo method will be called only if the object implements the IMoo interface.

            Cow bossie = new Cow("Bossie", 12);
            object mooer = bossie;
            MooIfYouCan(mooer);

            mooer = new Dog("Bert", 5);
            MooIfYouCan(mooer);
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About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

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