#1,051 – Implicit Reference Conversions

An implicit reference conversion is a conversion between reference types that is guaranteed to succeed and therefore does not require a cast operator.

Here are some examples:

            Dog dog = new Dog("Bowser");

            // From ref type to object
            object o1 = dog;

            // From ref type to dynamic
            dynamic dyn1 = dog;

            // From derived class to parent class
            Terrier terr = new Terrier("Jack");
            dog = terr;

            // From class to interface that class
            // implements
            IBark iBark = dog;

            // From a derived interface to
            // base interface
            IBarkWithStyle iBarkDerived = dog;
            iBark = iBarkDerived;

            // Covariant array conversion
            // Dog[] = Terrier[] ok because
            //    Dog = Terrier ok
            Terrier[] terriers = new Terrier[2];
            terriers[0] = new Terrier("Bobby");
            terriers[1] = new Terrier("Sydney");
            Dog[] dogs = terriers;

            // From array type to System.Array
            Array arr = terriers;

            // From array to IList<T>
            IList<Dog> dogList = terriers;

            // From any delegate-type to System.Delegate 
            // and the interfaces it implements
            MyStringHandlerDelegate del1 = HandleString;
            Delegate del2 = del1;

            // From null literal to any reference type
            Dog dog2 = null;

            // From any ref type to a ref type T if it has an 
            // implicit identity or reference conversion
            // to T0 and T0 has identity conversion to T.
            // E.g. can convert from Dog to object and
            //      from List to IEnumerable, so we can:
            List<Dog> somedogs = new List<Dog>();
            IEnumerable<object> genlist = somedogs;