#827 – Making a Deep Copy with a Copy Constructor

The semantics that you use within a copy constructor can be to make a shallow copy of an object or a deep copy.

In the example below, the copy constructor for Dog makes a deep copy of the object passed in.  In this case, that means that the new Dog that is created will also have a new instance of DogCollar object, copied from the DogCollar property of the original Dog object.

    public class Dog
        public string Name { get; set; }
        public int Age { get; set; }
        public DogCollar Collar { get; set; }

        // Constructor that takes individual property values
        public Dog(string name, int age)
            Name = name;
            Age = age;

        // Copy constructor (deep copy)
        public Dog(Dog otherDog)
            Name = otherDog.Name;
            Age = otherDog.Age;

            Collar = (otherDog.Collar != null) ?
                new DogCollar(otherDog.Collar.Length, otherDog.Collar.Width) :

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.

4 Responses to #827 – Making a Deep Copy with a Copy Constructor

  1. Elliott says:

    May I ask…. what is the advantage and disadvantage of implementing the copy constructor and ICloneable.Clone ?
    um… With talking about the best practice, which one you think should be more good to be used ?


  2. Alex says:

    Should “Name = otherDog.Name;” be “Name = String.Copy(otherDog.Name);” ? In order to make it a deep copy?

    • Sean says:

      I don’t think there’s a need. Since strings are immutable, both objects have the same copy and if you changed the value in otherDog, it wouldn’t affect the copy pointed to by the new object.

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