#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.

1057-001

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

2 Responses to #1,057 – Custom Explicit Conversions

  1. Pingback: Dew Drop – March 20, 2014 (#1747) | Morning Dew

  2. James Curran says:

    You’re using String.Format in a rather questionable way:
    string.Format(“Dog-” + value.ToString())

    could be better written as:

    string.Format(“Dog-{0}”, value)

    or

    “Dog-” + value.ToString()

    or even just:

    “Dog-” + value

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