#1,057 – Custom Explicit Conversions

You can define both implicit and explicit custom conversions for a type that you author.

In the code fragment below, we’ve defined an implicit conversion from int to Dog and an explicit conversion from Cow to Dog.

        // Implicitly convert from int to Dog
        public static implicit operator Dog(int value)
        {
            return new Dog(string.Format("Dog-" + value.ToString()), value);
        }

        // Explicitly convert from Cow to Dog
        public static explicit operator Dog(Cow cow)
        {
            return new Dog(string.Format(cow.Name + " IWasACow"), cow.Age);
        }

We can now do the following:

            Cow someCow = new Cow("Bessie", 3);

            // Implicit conversion from int to Dog
            Dog anotherDog = 42;

            // Explicit conversion from Cow to Dog
            Dog nowADog = (Dog)someCow;

If we try assigning a Cow instance to a variable of type Dog without the cast operator, we’ll get a compile-time error indicating that there is no implicit conversion between Cow and Dog.